1: Int J Hematol. 2005 Jul;82(1):1-8. Runx1/AML1 in normal and abnormal hematopoiesis. Yamagata T, Maki K, Mitani K. Section on Immunology and Immunogenetics, Joslin Diabetes Center, Harvard Medical School, Boston, MA, USA. Runx1/AML1 (also known as CBFA2 and PEBP23B) is a Runt family transcription factor critical for normal hematopoiesis. Runx1 forms a heterodimer with CBF3 and binds to the consensus PEBP2 sequence through the Runt domain. Runx1 enhances gene transcription by interacting with transcriptional coactivators such as p300 and CREB-binding protein. However, Runx1 can also suppress gene transcription by interacting with transcriptional corepressors, including mSin3A, TLE (mammalian homolog of Groucho), and histone deacetylases. Runx1 not only is critical for definitive hematopoiesis in the fetus but also is required for normal megakaryocytic maturation and T-lymphocyte and B-lymphocyte development in adult mice. Runx1 has been identified in leukemia-associated chromosomal translocations, including t(8;21) (Runx1-ETO/MTG8), t(16;21) (Runx1-MTG16), t(3;21) (Runx1-Evi1), t(12;21) (TEL-Runx1), and t(X;21) (Runx1-Fog2).The molecular mechanism of leukemogenesis by these fusion proteins is discussed. Various mutant mice expressing these fusion proteins have been created. However, expression of the fusion protein is not sufficient by itself to cause leukemia and likely requires additional events for leukemogenesis. Point mutations in a Runx1 allele cause haploinsufficiency and a biallelic null for Runx1, which are associated with familial platelet disorder with a propensity for acute myeloid leukemia (FPD/AML) and AML-M0, respectively. Thus, the correct protein structure and the precise dosage of Runx1 are essential for the maintenance of normal hematopoiesis. PMID: 16105753 [PubMed - in process] --------------------------------------------------------------- 2: Genes Chromosomes Cancer. 2005 Nov;44(3):265-70. Novel RUNX1-PRDM16 fusion transcripts in a patient with acute myeloid leukemia showing t(1;21)(p36;q22). Sakai I, Tamura T, Narumi H, Uchida N, Yakushijin Y, Hato T, Fujita S, Yasukawa M. First Department of Internal Medicine, Ehime University School of Medicine, Toon, Ehime 791-0295, Japan. ikusakai@m.ehime-u.ac.jp The t(1;21)(p36;q22) is a recurrent chromosome abnormality associated with therapy-related acute myeloid leukemia (AML). Although involvement of RUNX1 has been detected by fluorescence in situ hybridization analysis, the partner gene has not been reported previously. We identified a novel RUNX1 partner gene, MDS1/EVI1-like-gene 1 (PRDM16), in an AML patient with t(1;21). Alternative splicing of the fusion gene generates five different fusion transcripts. In two of them, the PRDM16 reading frame is maintained in the fusion with RUNX1, suggesting that the RUNX1-PRDM16 gene fusion results in the production of a protein that is highly homologous to the RUNX1-MDS1/EVI1 chimeric protein. It is suggested that PRDM16 and MDS1/EVI1 share a common molecular mechanism for the leukemogenesis of RUNX1-associated leukemia. Characterization of the RUNX1-PRDM16 fusion protein and comparison with the RUNX1-MDS1/EVI1 protein will facilitate the understanding of the mechanisms underlying RUNX1-associated leukemia. (c) 2005 Wiley-Liss, Inc. PMID: 16015645 [PubMed - in process] --------------------------------------------------------------- 3: Blood. 2005 Sep 15;106(6):2147-55. Epub 2005 May 24. Dysplastic definitive hematopoiesis in AML1/EVI1 knock-in embryos. Maki K, Yamagata T, Asai T, Yamazaki I, Oda H, Hirai H, Mitani K. Department of Hematology, Dokkyo University School of Medicine, 880 Kitakobayashi, Mibu-machi, Shimotsuga-gun, Tochigi 321-0293, Japan. The AML1/EVI1 chimeric gene is created by the t(3;21)(q26;q22) chromosomal translocation seen in patients with leukemic transformation of myelodysplastic syndrome or blastic crisis of chronic myelogenous leukemia. We knocked-in the AML1/EVI1 chimeric gene into mouse Aml1 genomic locus to explore its effect in developmental hematopoiesis in vivo. AML1/EVI1/+ embryo showed defective hematopoiesis in the fetal liver and died around embryonic day 13.5 (E13.5) as a result of hemorrhage in the central nervous system. The peripheral blood had yolk-sac-derived nucleated erythroblasts but lacked erythrocytes of the definitive origin. Although E12.5 fetal liver contained progenitors for macrophage only, E13.5 fetal liver contained multilineage progenitors capable of differentiating into dysplastic myelocyte and megakaryocyte. No erythroid progenitor was detected in E12.5 or E13.5 fetal liver. Hematopoietic progenitors from E13.5 AML1/EVI1/+ fetal liver were highly capable of self-renewal compared with those from wild-type liver. Maintained expression of PU.1 gene and decreased expression of LMO2 and SCL genes may explain the aberrant hematopoiesis in AML1/EVI1/+ fetal liver. PMID: 15914564 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 4: Oncogene. 2004 May 24;23(24):4263-9. Molecular mechanisms of leukemogenesis by AML1/EVI-1. Mitani K. Department of Hematology, Dokkyo University School of Medicine, Tochigi 321-0293, Japan. kinukom-tky@umin.ac.jp The AML1/EVI-1 chimeric gene is generated by the t(3;21)(q26;q22) translocation and plays a pivotal role in progression of hematopoietic stem cell malignancies such as chronic myelocytic leukemia and myelodysplastic syndrome. In AML1/EVI-1, an N-terminal half of AML1 including a runt homology domain is fused to the entire zinc-finger EVI-1 protein. AML1 is essential for hematopoietic cell development in fetal liver and its lineage-specific differentiation in adult. In contrast, EVI-1 is barely expressed in normal hematopoietic cells, but it is overexpressed in chronic myelocytic leukemia in blastic crisis and myelodysplastic syndrome-derived leukemia. There are at least four mechanisms identified in AML1/EVI-1 fusion protein that possibly lead into malignant transformation of hematopoietic stem cells. Firstly, AML1/EVI-1 exerts dominant-negative effects over AML1-induced transcriptional activation. Although target genes repressed by AML1/EVI-1 are still not known, binding competition to a specific DNA sequence and histone deacetylase recruitment through a co-repressor CtBP in EVI-1 part are conceivable underlying mechanisms for the dominant-negative effects. Secondly, AML1/EVI-1 interferes with TGF beta signaling and antagonizes the growth-inhibitory effects of TGF beta. The first zinc-finger domain of EVI-1 associates with Smad3, a TGF beta signal transducer, and represses its transcriptional activity by recruiting histone deacetylase through CtBP that interacts with EVI-1. Thirdly, AML1/EVI-1 blocks JNK activity and prevents stress-induced apoptosis. AML1/EVI-1 associates with JNK through the first zinc-finger domain of EVI-1 and disturbs the association between JNK and its substrates. Lastly, AML1/EVI-1 enhances AP-1 activity by activating the c-Fos promoter depending on the second zinc-finger domain of EVI-1, and promotes cell proliferation. All these functions cooperatively contribute to the malignant transformation of the hematopoietic stem cells by AML1/EVI-1. Publication Types: Review Review, Tutorial PMID: 15156182 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 5: Oncogene. 2004 Jan 15;23(2):569-79. Both AML1 and EVI1 oncogenic components are required for the cooperation of AML1/MDS1/EVI1 with BCR/ABL in the induction of acute myelogenous leukemia in mice. Cuenco GM, Ren R. Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, MA 02454-9110, USA. We have previously shown that BCR/ABL, a fusion protein generated by the t(9;22)(q34;q11) translocation found in the vast majority of chronic myelogenous leukemia (CML), cooperates with AML1/MDS1/EVI1 (AME), a fusion transcription factor generated by a t(3;21)(q26;q22) translocation identified as a secondary mutation in some cases of CML during the blast phase (CML-BC), in the rapid induction of an acute myelogenous leukemia (AML) in mice. In this study, we evaluated the leukemogenic potential of EVI1-, MDS1/EVI1- and AML1-related oncoproteins (AML1Delta, AML1/MDS1). We found that ectopic expression of either EVI1 or MDS1/EVI1 impaired hematopoiesis. However, neither EVI1 nor MDS1/EVI1 was sufficient for inducing AML in mice, although EVI1 did induce some hematologic neoplasia other than AML with a low efficiency. In addition, unlike AME, none of the EVI1- or AML1-related oncoproteins examined were capable of fully cooperating with BCR/ABL in the induction of AML. The results indicate that both the AML1 and EVI1 oncogenic components are required for the leukemogenic potential of AME and for the cooperation of AME and BCR/ABL in the induction of AML. PMID: 14724585 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 6: Cancer Sci. 2003 Oct;94(10):841-6. Role of AML1/Runx1 in the pathogenesis of hematological malignancies. Kurokawa M, Hirai H. Department of Hematology and Oncology, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo113-8655, Japan. AML1/Runx1, originally identified as a gene located at the breakpoint of the t(8;21) translocation, encodes one of the two subunits forming a heterodimeric transcription factor. AML1 contains a highly evolutionally conserved domain called the Runt domain, responsible for both DNA binding and heterodimerization with the partner protein, CBFbeta. AML1 is widely expressed in all hematopoietic lineages, and regulates the expression of a variety of hematopoietic genes. Numerous studies have shown that AML is a critical regulator of hematopoietic development. In addition, AML1 and CBFbeta are frequent targets for chromosomal translocation in human leukemia. Translocations lead to the generation of fusion proteins, which play a causative role for the development of leukemia, primarily by inhibiting AML1 function. Point mutations that impair AML1 function are also associated with familial and sporadic leukemias. Loss of AML1 function is thus implicated in a number of leukemias through multiple pathogenic mechanisms. However, AML1-related translocations or haploinsufficiency of AML1 are not immediately leukemogenic in animal models, suggesting that additional genetic events are required for the development of full-blown leukemia. Publication Types: Review Review, Tutorial PMID: 14556655 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 7: Oncogene. 2002 Apr 18;21(17):2695-703. The t(3;21) fusion product, AML1/Evi-1 blocks AML1-induced transactivation by recruiting CtBP. Izutsu K, Kurokawa M, Imai Y, Ichikawa M, Asai T, Maki K, Mitani K, Hirai H. Department of Hematology and Oncology, Graduate School of Medicine, University of Tokyo, Tokyo 113-8655, Japan. AML1/Evi-1 is a chimeric protein that is derived from t(3;21), found in blastic transformation of chronic myelogenous leukemia. It is composed of the N-terminal AML1 portion with the DNA-binding Runt domain and the C-terminal Evi-1 portion. It has been shown to dominantly repress AML1-induced transactivation. The mechanism for it has been mainly attributed to competition with AML1 for the DNA-binding and for the interaction with PEBP2beta (CBFbeta), a partner protein which heterodimerizes with AML1. It was recently found that Evi-1 interacts with C-terminal binding protein (CtBP) to repress TGFbeta-induced transactivation. Here, we demonstrate that AML1/Evi-1 interacts with CtBP in SKH1 cells, a leukemic cell line which endogenously overexpresses AML1/Evi-1 and that AML1/Evi-1 requires the interaction with CtBP to repress AML1-induced transactivation. The association with CtBP is also required when AML1/Evi-1 blocks myeloid differentiation of 32Dcl3 cells induced by granulocyte colony-stimulating factor. Taken together, it is suggested that one of the mechanisms for AML1/Evi-1-associated leukemogenesis should be an aberrant recruitment of a corepressor complex by the chimeric protein. PMID: 11965542 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 8: Oncogene. 2001 Dec 13;20(57):8236-48. Cooperation of BCR-ABL and AML1/MDS1/EVI1 in blocking myeloid differentiation and rapid induction of an acute myelogenous leukemia. Cuenco GM, Ren R. Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, MA 02454, USA. The development of acute myelogenous leukemia (AML), which is characterized by a block of myeloid differentiation, is a multi-step process that involves several genetic abnormalities, but the molecular mechanisms by which these genetic alterations cooperate in leukemogenesis are poorly understood. The human chronic myelogenous leukemia (CML) is a model for multi-step leukemogenesis. BCR-ABL, a constitutively active tyrosine kinase, is a fusion protein generated by the t(9;22)(q34;q11) translocation found in the vast majority of CML patients. BCR-ABL efficiently induces a myeloproliferative disorder (MPD) in mice, but progression to CML blast phase requires additional mutations. The AML1/MDS1/EVI1 (AME) transcription factor fusion protein, is a product of the human t(3;21)(q26;q22) translocation found as a secondary mutation in some cases of CML during the blast phase. We have previously shown that AME can induce an AML in mice but with a greatly extended latency, suggesting a requirement for additional mutations. Here we demonstrate that AME alone does not block myeloid differentiation in vivo during the 4-month pre-leukemia stage, yet co-expression of BCR-ABL and AME in mice can block myeloid differentiation and rapidly induce an AML. Our results suggest that block of myeloid differentiation and induction of AML involves cooperation between mutations that dysregulate protein tyrosine kinase signaling and those that disrupt hematopoietic gene transcription. PMID: 11781838 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 9: Cancer Genet Cytogenet. 2001 Sep;129(2):155-60. A unique AML1 (CBF2A) rearrangement, t(1;21)(p32;q22), observed in a patient with acute myelomonocytic leukemia. Cherry AM, Bangs CD, Jones P, Hall S, Natkunam Y. Department of Pathology, Stanford University Medical Center, Stanford, CA 94305, USA. athena.cherry@medcenter.stanford.edu The AML1 (CBFA2) gene is the most frequent target of chromosomal rearrangements observed in human acute leukemia. These rearrangements include the commonly reported t(8;21)(q22;q22) or AML1/ETO fusion in AML-M2, the t(3;21)(q26;q22) or AML1 fusion with one of three genes, MDS1, EAP or EVI1, in therapy-related AML and MDS, as well as in blast crisis in CML and the t(12;21)(p13;q22) or TEL/AML1 fusion in B-cell ALL. In addition to the t(3;21), other AML1 translocations have also been reported in therapy-related MDS and AML, particularly after treatment with topoisomerase II inhibitors. AML1 gene rearrangements have also been observed less frequently with numerous other chromosomal partners. Here, we describe a patient with AML-M4 and a previously unreported rearrangement involving the AML1 locus and an unknown locus on the short arm of chromosome 1 at 1p32. Publication Types: Case Reports PMID: 11566347 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 10: Cytogenet Cell Genet. 2000;91(1-4):52-6. Fusion genes in leukemia: an emerging network. Bohlander SK. Institute of Human Genetics, Gottingen, Germany. sbohlan@gwdg.de The molecular analysis of recurring chromosome rearrangements, especially of translocations and inversions, has provided us with valuable insight into the pathogenesis of hematological malignancies. Many translocations result in the fusion of genes located at the translocation breakpoints. In recent years we have witnessed a rapid rise in the number of chromosome translocations in leukemias being characterized at the molecular level. However, the number of genes being newly identified as translocation fusion genes has not risen at the same pace. This is due to the fact that several genes are involved in more than one translocation forming fusion genes with a number of other partner genes. Not only does one find star-shaped topologies, with one gene forming fusions with several others (e.g. ETV6/PDGFRB, ETV6/JAK2, ETV6/ABL etc.), but also networks connecting several genes with more than one fusion partner (e.g. ETV6/RUNX1 (AML1), RUNX1/CBFA2T1 (ETO), ETV6/EVI1, RUNX1/EVI1, ETV6/ABL, BCR/ABL). The emergence of such networks with the "recycling" of genes in new fusion combinations suggests that there is a rather limited number of genes which can be altered to cause leukemia. Copyright 2001 S. Karger AG, Basel Publication Types: Review Review, Tutorial PMID: 11173830 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 11: Proc Natl Acad Sci U S A. 2000 Feb 15;97(4):1760-5. Human AML1/MDS1/EVI1 fusion protein induces an acute myelogenous leukemia (AML) in mice: a model for human AML. Cuenco GM, Nucifora G, Ren R. Rosenstiel Basic Medical Sciences Research Center, Department of Biology, Brandeis University, Waltham, MA 02454, USA. The human t(3;21)(q26;q22) translocation is found as a secondary mutation in some cases of chronic myelogenous leukemia during the blast phase and in therapy-related myelodysplasia and acute myelogenous leukemia. One result of this translocation is a fusion between the AML1, MDS1, and EVI1 genes, which encodes a transcription factor of approximately 200 kDa. The role of the AML1/MDS1/EVI1 (AME) fusion gene in leukemogenesis is largely unknown. In this study, we analyzed the effect of the AME fusion gene in vivo by expressing it in mouse bone marrow cells via retroviral transduction. We found that mice transplanted with AME-transduced bone marrow cells suffered from an acute myelogenous leukemia (AML) 5-13 mo after transplantation. The disease could be readily transferred into secondary recipients with a much shorter latency. Morphological analysis of peripheral blood and bone marrow smears demonstrated the presence of myeloid blast cells and differentiated but immature cells of both myelocytic and monocytic lineages. Cytochemical and flow cytometric analysis confirmed that these mice had a disease similar to the human acute myelomonocytic leukemia. This murine model for AME-induced AML will help dissect the molecular mechanism of AML and the molecular biology of the AML1, MDS1, and EVI1 genes. PMID: 10677531 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 12: Tanpakushitsu Kakusan Koso. 2000 Jan;45(1):33-9. [Leukemogenesis by the AML1/EVI-1 chimeric protein] [Article in Japanese] Mitani K, Hirai H. Department of Hematology & Oncology, Graduate School of Medicine, University of Tokyo, Japan. Publication Types: Review Review, Tutorial PMID: 10643333 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 13: Leukemia. 1999 Dec;13(12):1932-42. Leukemogenesis by CBF oncoproteins. Friedman AD. Division of Pediatric Oncology, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. The AML1 and CBFbeta subunits of core binding factor (CBF) are involved in several chromosomal abnormalities frequently associated with acute leukemias. As a result, the CBFbeta-SMMHC, AML1-ETO and AML1-MDS1/EVI1 fusion proteins are expressed in subsets of acute myeloid leukemia, and TEL-AML1 is expressed in B-lineage acute lymphocytic leukemia. These CBF oncoproteins likely contribute to leukemogenesis in part by inhibiting endogenous CBF. As a result they are expected to inhibit differentiation and perhaps apoptosis. In addition, the domains unique to each fusion protein may also contribute to leukemogenesis via unique mechanisms. Publication Types: Review Review, Tutorial PMID: 10602413 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 14: Rinsho Ketsueki. 1999 Jun;40(6):518-20. [Detection of t(3 ; 21) (q26 ; q22) with AML1/EVI1 mRNA during progression of myelodysplastic syndrome to acute myeloid leukemia] [Article in Japanese] Choi I, Goto T, Nagano M, Muta K, Yufu Y, Uike N, Kozuru M, Abe Y, Nisimura J. Department of Hematology, National Kyushu Cancer Center. A 74-year-old woman had myelodysplastic syndrome (MDS) in 1986. In June 1994, she suffered exacerbation of pancytopenia with no chromosomal abnormalities, but AML1/EVI1 chimeric mRNA was detected by RT-PCR. Two months later, an increase in bone marrow blasts (5%) was noted, and chromosomal analysis detected t(3 ; 21) (q26 ; 22), del(7) (q22), del(11) (q23). In 1995, the marrow blasts increased to 30% and the patient died of disease progression. The AML1/EVI1 gene has been shown to cause blast crisis in chronic myelogenous leukemia. This case suggested that the AML1/EVI1 gene may be involved in the progression of MDS together with del(7) (q22) and del(11) (q23). Publication Types: Case Reports PMID: 10422292 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 15: Leukemia. 1999 Mar;13(3):348-57. MDS1/EVI1 enhances TGF-beta1 signaling and strengthens its growth-inhibitory effect but the leukemia-associated fusion protein AML1/MDS1/EVI1, product of the t(3;21), abrogates growth-inhibition in response to TGF-beta1. Sood R, Talwar-Trikha A, Chakrabarti SR, Nucifora G. Oncology Institute, Loyola University Medical Center, Maywood, IL 60153, USA. MDS1/EVI1, located on chromosome 3 band q26, encodes a zinc-finger DNA-binding transcription activator not detected in normal hematopoietic cells but expressed in several normal tissues. MDS1/EVI1 is inappropriately activated in myeloid leukemias following chromosomal rearrangements involving band 3q26. The rearrangements lead either to gene truncation, and to expression of the transcription repressor EVI1, as seen in the t(3;3)(q21;q26) and inv(3)(q21q26), or to gene fusion, as seen in the t(3;21)(q26;q22) which results in the fusion protein AML1/MDS1/EVI1. This fusion protein contains the DNA-binding domain of the transcription factor AML1 fused in-frame to the entire MDS1/EVI1 with the exclusion of its first 12 amino acids. In this report, we have analyzed the response of the hematopoietic precursor cell line 32Dcl3, expressing either the normal protein MDS1/EVI1 or the fusion protein AML1/MDS1/EVI1, to factors that control cell differentiation or cell replication. The 32Dcl3 cells are IL-3-dependent for growth and they differentiate into granulocytes when exposed to G-CSF. They are growth-inhibited by TGF-beta1. We show that whereas the expression of MDS1/EVI1 has no effect on granulocytic differentiation induced by G-CSF, expression of AML1/MDS1/EVI1 blocks differentiation resulting in cell death. This effect is similar to that previously described by others for 32Dcl3 cells that express transgenic Evil. Furthermore, we show that whereas the expression of the fusion protein AML1/MDS1/EVI1 completely abrogates the growth-inhibitory effect of TGF-beta1 and allows 32Dcl3 cells to proliferate, expression of the normal protein MDS1/EVI1 has the opposite effect, and it strengthens the response of cells to the growth-inhibitory effect of TGF-beta1. By using the yeast two-hybrid system, we also show that EVI1 (contained in its entirety in MDS1/EVI1 and AML1/MDS1/EVI1) physically interacts with SMAD3, which is an intracellular mediator of TGF-beta1 signaling. Finally, we have correlated the response of the cells to G-CSF or TGF-beta1 with the ability of the normal and fusion proteins to activate or repress promoters which they can directly regulate by binding to the promoter site. We propose that mutations of MDS1/EVI1 either by gene truncation resulting in the transcription repressor EVI1 or by gene fusion to AML1 lead to an altered cellular response to growth and differentiation factors that could result in leukemic transformation. The different response of myeloid cells ectopically expressing the normal or the fusion protein to G-CSF and TGF-beta1 could depend on the different transactivation properties of these proteins resulting in divergent expression of downstream genes regulated by the two proteins. PMID: 10086725 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 16: Blood. 1998 Dec 1;92(11):4003-12. The t(3;21) fusion product, AML1/Evi-1, interacts with Smad3 and blocks transforming growth factor-beta-mediated growth inhibition of myeloid cells. Kurokawa M, Mitani K, Imai Y, Ogawa S, Yazaki Y, Hirai H. Department of Hematology & Oncology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan. The t(3;21)(q26;q22) chromosomal translocation associated with blastic crisis of chronic myelogenous leukemia results in the formation of the AML1/Evi-1 chimeric protein, which is thought to play a causative role in leukemic transformation of hematopoietic cells. Here we show that AML1/Evi-1 represses growth-inhibitory signaling by transforming growth factor-beta (TGF-beta) in 32Dcl3 myeloid cells. The activity of AML1/Evi-1 to repress TGF-beta signaling depends on the two separate regions of the Evi-1 portion, one of which is the first zinc finger domain. AML1/Evi-1 interacts with Smad3, an intracellular mediator of TGF-beta signaling, through the first zinc finger domain, and represses the Smad3 activity, as Evi-1 does. We also show that suppression of endogenous Evi-1 in leukemic cells carrying inv(3) restores TGF-beta responsiveness. Taken together, AML1/Evi-1 acts as an inhibitor of TGF-beta signaling by interfering with Smad3 through the Evi-1 portion, and both AML1/Evi-1 and Evi-1 repress TGF-beta-mediated growth suppression in hematopoietic cells. Thus, AML1/Evi-1 may contribute to leukemogenesis by specifically blocking growth-inhibitory signaling of TGF-beta in the t(3;21) leukemia. PMID: 9834202 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 17: Blood. 1998 Oct 15;92(8):2879-85. CBFA2(AML1) translocations with novel partner chromosomes in myeloid leukemias: association with prior therapy. Roulston D, Espinosa R 3rd, Nucifora G, Larson RA, Le Beau MM, Rowley JD. Section of Hematology/Oncology, Department of Medicine, and the Cancer Research Center, The University of Chicago Pritzker School of Medicine, Chicago, IL, USA. CBFA2(AML1) has emerged as a gene critical in hematopoiesis; its protein product forms the DNA-binding subunit of the heterodimeric core-binding factor (CBF) that binds to the transcriptional regulatory regions of genes, some of which are active specifically in hematopoiesis. CBFA2 forms a fusion gene with ETO and MDS1/EVI1 in translocations in myeloid leukemia and with ETV6(TEL) in the t(12;21) common in childhood pre-B acute lymphoblastic leukemia. We have analyzed samples from 30 leukemia patients who had chromosome rearrangements involving 21q22 by using fluorescence in situ hybridization (FISH). Our analysis showed that 7 of them involved CBFA2 and new translocation partners. Two patients had a t(17;21)(q11.2;q22), whereas the other 5 had translocations involving 1p36, 5q13, 12q24, 14q22, or 15q22. Five of these novel breakpoints in CBFA2 occurred in intron 6; this same intron is involved in the t(3;21). One breakpoint mapped to the t(8;21) breakpoint region in intron 5, and 1 mapped 5' to that region. All 7 CBFA2 rearrangements resulted from balanced translocations. All 7 patients had myeloid disorders (acute myeloid leukemia or myelodysplastic syndrome); 2 were de novo and 5 had treatment histories that included topoisomerase II targeting agents. The association of therapy-related disorders with translocations involving CBFA2 was significant by Fisher's exact test (P < .003). These results provide further evidence that this region of CBFA2 is susceptible to breakage in cells exposed to topoisomerase II inhibitors. Copyright 1998 by The American Society of Hematology. PMID: 9763573 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 18: Blood. 1998 Mar 1;91(5):1688-99. The AML1/ETO(MTG8) and AML1/Evi-1 leukemia-associated chimeric oncoproteins accumulate PEBP2beta(CBFbeta) in the nucleus more efficiently than wild-type AML1. Tanaka K, Tanaka T, Kurokawa M, Imai Y, Ogawa S, Mitani K, Yazaki Y, Hirai H. Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan. AML1, a gene on chromosome 21 encoding a transcription factor, is disrupted in the (8;21)(q22;q22) and (3;21)(q26;q22) chromosomal translocations associated with myelogenous leukemias; as a result, chimeric proteins AML1/ETO(MTG8) and AML1/Evi-1 are generated, respectively. To clarify the roles of AML1/ETO(MTG8) and AML1/Evi-1 in leukemogenesis, we investigated subcellular localization of these chimeric proteins by immunofluorescence labeling and subcellular fractionation of COS-7 cells that express these chimeric proteins. AML1/ETO(MTG8) and AML1/Evi-1 are nuclear proteins, as is wild-type AML1. Polyomavirus enhancer binding protein (PEBP)2beta(core binding factor [CBF]beta), a heterodimerizing partner of AML1 that is located mainly in the cytoplasm, was translocated into the nucleus with dependence on the runt domain of AML1/ETO(MTG8) or AML1/Evi-1 when coexpressed with these chimeric proteins. When a comparable amount of wild-type AML1 or the chimeric proteins was coexpressed with PEBP2beta(CBFbeta), more of the cells expressing the chimeric proteins showed the nuclear accumulation of PEBP2beta(CBFbeta), as compared with the cells expressing wild-type AML1. We also showed that the chimeric proteins associate with PEBP2beta(CBFbeta) more effectively than wild-type AML1. These data suggest that the chimeric proteins are able to accumulate PEBP2beta(CBFbeta) in the nucleus more efficiently than wild-type AML1, probably because of the higher affinities of the chimeric proteins for PEBP2beta(CBFbeta) than that of wild-type AML1. These effects of the chimeric proteins on the cellular distribution of PEBP2beta(CBFbeta) possibly cause the dominant negative properties of the chimeric proteins over wild-type AML1 and account for one of the mechanisms through which these chimeric proteins contribute to leukemogenesis. PMID: 9473235 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 19: Cancer Res. 1997 Sep 15;57(18):3914-9. Activation of a novel gene in 3q21 and identification of intergenic fusion transcripts with ecotropic viral insertion site I in leukemia. Pekarsky Y, Rynditch A, Wieser R, Fonatsch C, Gardiner K. Eleanor Roosevelt Institute, Denver, Colorado 80206, USA. We have identified a novel gene, GR6, located within the leukemia breakpoint region of 3q21, that is normally expressed in early fetal development but not in adult peripheral blood. GR6 is activated in the UCSD-AML1 cell line and in a leukemic sample, both of which carry a t(3;3)(q21;q26). In UCSD-AML1, we have also identified fusion transcripts between the ecotropic viral insertion site I (EVI1) gene in 3q26 and GR6 and between EVI1 and Ribophorin I that maps 30 kb telomeric to GR6 in 3q21. All fusions splice the 5' ends of the 3q21 genes into exon 2 of the EVI1 gene, an event that is similar to the normal intergenic splicing of MDS1-EVI1 and to those previously documented in leukemias with t(3;21) and t(3;12), in which acute myelogenous leukemia 1-EVI1 fusions and ETV6-EVI1 fusions, respectively, occur. The Ribophorin I-EVI1 fusion in particular may be a common occurrence in t(3;3). PMID: 9307271 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 20: Haematologica. 1997 May-Jun;82(3):364-70. The AML1 gene: a transcription factor involved in the pathogenesis of myeloid and lymphoid leukemias. Lo Coco F, Pisegna S, Diverio D. Department of Human Biopathology, University La Sapienza of Rome, Italy. lococo@dbu.uniroma1.it BACKGROUND AND OBJECTIVE: The AML1 gene was identified in 1991 by cloning the t(8;21) chromosome translocation associated with FAB M2 acute myeloid leukemia (AML). AML1 encodes a nuclear transcription factor (TF) which shows homology in its 5' part with the Drosophila melanogaster segmentation gene, runt, and contains a transactivation domain in the carboxyterminal portion. In the t(8;21), AML1 is fused to the ETO (MTG8) gene, resulting in a hybrid AML1/ETO mRNA, which in turn is translated into a chimeric protein. The objective of this article is to review here the main structural and biological features of AML1 and of its fusion products, with special focus on their clinical correlations and their potential usefulness for prognostic and monitoring studies in human leukemia. EVIDENCE AND INFORMATION SOURCES: The material examined in the present review includes articles and abstracts published in journals covered by the Science Citation Index and Medline. STATE OF ART: The normal AML-1 protein forms the alpha-subunit of the heterodimeric TF core binding factor (or CBF), whose beta-subunit is encoded by the CBF beta gene on chromosome 16q22. CBF beta is rearranged and fused to the MYH11 gene in the AML M4Eo-associated inv(16) aberration. Thus, the two most common chromosome abnormalities of AML, i.e. t(8;21) and inv(16), affect the two subunits of the same target protein. This suggests that the wild type CBF must exert an important role in the control of myeloid cell growth and/or differentiation. Evidence that AML1 is a pivotal regulator of definitive hematopoiesis has been recently provided by analyzing AML1 knockout mice. The chromosome region 21q22, where AML1 maps, is involved in several other karyotypic aberrations, such as the t(3;21) translocation associated with a subset of therapy-related myelodysplastic syndromes and AML, and the blast phase of chronic myelogenous leukemia. In this abnormality, three distinct genes: EVI1, EAP, MDS1, located on chromosome band 3q26, have been identified that may recombine with AML1. Finally, the recently cloned t(12;21) translocation has been found to involve the TEL gene (coding for a novel TF) on 12p13, and AML1 on 21q22. This alteration, which results in the production of a TEL/AML1 chimeric protein, is restricted to pediatric B-lineage acute lymphoid leukemia (ALL), where it represents the most frequent molecular defect known to date (up to 25% of cases). Strikingly, the same t(12;21) is identified in only 0.05% of pediatric B-lineage ALL cases analyzed by conventional karyotyping. Other relevant characteristics of TEL/AML1-positive ALL are frequent deletion of the other TEL allele and association with an excellent prognostic outcome. PERSPECTIVES: It is expected that future studies will provide more detailed information on the leukemogenic effect of AML1 alterations, and better define the prognostic relevance of detecting the hybrid proteins formed by this gene at diagnosis and during remission. Publication Types: Review Review, Tutorial PMID: 9234595 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 21: Leukemia. 1997 Apr;11 Suppl 3:503-5. Molecular mechanism of blastic crisis in chronic myelocytic leukemia. Mitani K. Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan. The t(3;21)(q26;q22), which is usually found in blastic crisis of chronic myelocytic leukemia or myelodysplastic syndrome-derived leukemia, produces an AML1/EVI-1 fusion protein of 180 kD containing amino-terminal half of AML1 including a runt homology domain which is fused to the entire of zinc finger EVI-1 protein. Thus, AML1/EVI-1 fusion protein is a chimeric transcription factor including a runt homology domain from AML1 and two zinc finger domains from EVI-1, totally three DNA binding domains, and an acidic domain from EVI-1. The AML1/EVI-1 fusion protein possesses the dual functions, namely, differentiation block and stimulation of proliferation. The ability of differentiation block depends on the runt homology domain in the AML1 part and the effect to stimulate proliferation depends on the second zinc finger domain in the EVI-1 portion. The AML1/EVI-1 could play an important role in leukemic progression of chronic myelocytic leukemia by these dual functions as a transcription factor. PMID: 9209439 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 22: Leukemia. 1997 Apr;11 Suppl 3:273-8. Rearrangements of the AML1/CBFA2 gene in myeloid leukemia with the 3;21 translocation: in vitro and in vivo studies. Zent C, Rowley JD, Nucifora G. Department of Medicine, University of Chicago, IL., USA. AML1 is involved at the breakpoint of chromosome 21 band q22 in several recurring chromosomal translocations associated with myeloid and lymphoid leukemias. AML1 corresponds to CBFA2, and encodes one of the DNA-binding subunits of the enhancer core binding factor CBF. Other members of this family of DNA-binding proteins are CBFA1 and CBFA3, also known as AML3 and AML2. The three proteins are characterized by a highly conserved domain (runt domain, > 90% homology) at the amino end that is necessary for DNA-binding and protein dimerization, and by a unique domain at the carboxyl end that is necessary for transactivation. Two recurring chromosomal translocations involving AML1 associated with myeloid leukemias are the t(8;21)(q22;q22), seen in 20% of patients with acute myeloid leukemia (AML) M2, and the t(3;21)(q26;q22), that occurs in myeloid leukemias primarily following treatment with topoisomerase II inhibitors. In five patients with a t(3;21) whom we studied, AML1 is interrupted by the translocation breakpoint between the runt domain and the transactivation domain, and is fused to two genes on chromosome band 3q26: EAP, which encodes the ribosomal protein L22, and MDS1, which encodes a small polypeptide of unknown function. In one of the five patients we studied, a fusion with a third gene EVI1 also occurs. The fusion of EAP to AML1 is not in frame, and leads to a protein that is terminated shortly after the fusion junction by introduction of a stop codon. The fusion of AML1 to MDS1 is in frame, and adds 127 codons to the interrupted AML1. Thus, in the five cases that we studied, the 3;21 translocation results in expression of two coexisting chimeric mRNAs which contain the identical runt domain at the 5' region, but differ in the 3' region. In addition, the chimeric junction AML1/MDS1/EVII has been detected in cells from one of our patients with the 3;21 translocation. Several genes necessary for myeloid lineage differentiation contain the target sequence for AML1 in their regulatory regions. We have compared the normal AML1 to AML1/MDS1 and AML1/EAP as transcriptional regulators of the CSF1R promoter which contains the CBF target sequence. Our results indicate that whereas the normal AML1 can activate the promoter, the chimeric proteins compete with the normal AML1 and repress expression from the CSF1R promoter. To determine the role of the chimeric proteins in cell growth, we expressed their cDNA in rat fibroblasts. When either fusion gene is expressed, the cells lose contact inhibition and form foci over the monolayer. However, only cells expressing AML1/MDS1 grow as large tumors in nude mice. Thus, although both chimeric genes have similar effects in transactivation of the CSF1R promoter, they affect cell growth as tumor promoters differently in vivo. PMID: 9209363 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 23: Proc Natl Acad Sci U S A. 1996 Feb 20;93(4):1642-7. Intergenic splicing of MDS1 and EVI1 occurs in normal tissues as well as in myeloid leukemia and produces a new member of the PR domain family. Fears S, Mathieu C, Zeleznik-Le N, Huang S, Rowley JD, Nucifora G. Department of Molecular Genetics and Cellular Biology, The University of Chicago, IL 60637, USA. The EVI1 gene, located at chromosome band 3q26, is overexpressed in some myeloid leukemia patients with breakpoints either 5' of the gene in the t(3;3)(q21;q26) or 3' of the gene in the inv(3)(q21q26). EVI1 is also expressed as part of a fusion transcript with the transcription factor AML1 in the t(3;21)(q26;q22), associated with myeloid leukemia. In cells with t(3;21), additional fusion transcripts are AML1-MDS1 and AML1-MDS1-EVI1. MDS1 is located at 3q26 170-400 kb upstream (telomeric) of EVI1 in the chromosomal region in which some of the breakpoints 5' of EVI1 have been mapped. MDS1 has been identified as a single gene as well as a previously unreported exon(s) of EVI1 We have analyzed the relationship between MDS1 and EVI1 to determine whether they are two separate genes. In this report, we present evidence indicating that MDS1 exists in normal tissues both as a unique transcript and as a normal fusion transcript with EVI1, with an additional 188 codons at the 5' end of the previously reported EVI1 open reading frame. This additional region has about 40% homology at the amino acid level with the PR domain of the retinoblastoma-interacting zinc-finger protein RIZ. These results are important in view of the fact that EVI1 and MDS1 are involved in leukemia associated with chromosomal translocation breakpoints in the region between these genes. PMID: 8643684 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 24: Proc Natl Acad Sci U S A. 1996 Feb 6;93(3):1044-8. The chimeric genes AML1/MDS1 and AML1/EAP inhibit AML1B activation at the CSF1R promoter, but only AML1/MDS1 has tumor-promoter properties. Zent CS, Mathieu C, Claxton DF, Zhang DE, Tenen DG, Rowley JD, Nucifora G. Department of Medicine, University of Chicago, IL 60637, USA. The (3;21)(q26;q22) translocation associated with treatment-related myelodysplastic syndrome, treatment-related acute myeloid leukemia, and blast crisis of chronic myeloid leukemia results in the expression of the chimeric genes AML1/EAP, AML1/MDS1, and AML1/EVI1. AML1 (CBFA2), which codes for the alpha subunit of the heterodimeric transcription factor CBF, is also involved in the t(8;21), and the gene coding for the beta subunit (CBFB) is involved in the inv(16). These are two of the most common recurring chromosomal rearrangements in acute myeloid leukemia. CBF corresponds to the murine Pebp2 factor, and CBF binding sites are found in a number of eukaryotic and viral enhancers and promoters. We studied the effects of AML1/EAP and AML1/MDS1 at the AML1 binding site of the CSF1R (macrophage-colony-stimulating factor receptor gene) promoter by using reporter gene assays, and we analyzed the consequences of the expression of both chimeric proteins in an embryonic rat fibroblast cell line (Rat1A) in culture and after injection into athymic nude mice. Unlike AML1, which is an activator of the CSF1R promoter, the chimeric proteins did not transactivate the CSF1R promoter site but acted as inhibitors of AML1 (CBFA2). AML1/EAP and AML1/MDS1 expressed in adherent Rat1A cells decreased contact inhibition of growth, and expression of AML1/MDS1 was associated with acquisition of the ability to grow in suspension culture. Expression of AML1/MDS1 increased the tumorigenicity of Rat1A cells injected into athymic nude mice, whereas AML1/EAP expression prevented tumor growth. These results suggest that expression of AML1/EAP and AML1/MDS1 can interfere with normal AML1 function, and that AML1/MDS1 has tumor-promoting properties in an embryonic rat fibroblast cell line. PMID: 8577711 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 25: Br J Haematol. 1996 Feb;92(2):429-31. t(3;21)(q26;q22) with AML1 rearrangement in a de novo childhood acute monoblastic leukaemia. Johansson B, Fioretos T, Garwicz S, Heim S, Mitelman F. Department of Clinical Genetics, Lund University Hospital, Sweden. t(3;21)(q26;q22) is a recurrent chromosomal abnormality in Philadelphia-positive chronic myeloid leukaemia in blast crisis and in treatment-related myelodysplastic syndrome and acute myeloid leukaemia. The molecular consequences of the t(3;21) are presently being unravelled; various transcripts between the AML1 gene in 21q22 and several unrelated genes, i.e. EAP, EVI1 and MDS1, in 3q26 are generated, resulting in the formation of a chimaeric transcription factor. The t(3;21) has only rarely been described in de novo leukaemias and never before in an acute leukaemia in a child. We here present the clinical, cytogenetic and molecular genetic findings in a boy with a de novo acute monoblastic leukaemia with t(3;21)(q26;q22) and AML1 rearrangement. Publication Types: Case Reports PMID: 8603012 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 26: Curr Top Microbiol Immunol. 1996;211:243-52. Rearrangement of the AML1/CBFA2 gene in myeloid leukemia with the 3;21 translocation: expression of co-existing multiple chimeric genes with similar functions as transcriptional repressors, but with opposite tumorigenic properties. Zent C, Kim N, Hiebert S, Zhang DE, Tenen DG, Rowley JD, Nucifora G. Department of Medicine, University of Chicago, IL, USA. Several recurring chromosomal translocations involve the AML1 gene at 21q22 in myeloid leukemias resulting in fusion mRNAs and chimeric proteins between AML1 and a gene on the partner chromosome. AML1 corresponds to CBFA2, one of the DNA-binding subunits of the enhancer core binding factor CBF. Other CBF DNA-binding subunits are CBFA1 and CBFA3, also known as AML3 and AML2. AML1, AML2 and AML3 are each characterized by a conserved domain at the amino end, the runt domain, that is necessary for DNA-binding and protein dimerization, and by a transactivation domain at the carboxyl end. AML1 was first identified as the gene located at the breakpoint junction of the 8;21 translocation associated with acute myeloid leukemia. The t(8;21)(q22;q22) interrupts AML1 after the runt homology domain, and fuses the 5' part of AML1 to almost all of ETO, the partner gene on chromosome 8. AML1 is an activator of several myeloid promoters; however, the chimeric AML1/ETO is a strong repressor of some AML1-dependent promoters. AML1 is also involved in the t(3;21)(q26;q22), that occurs in myeloid leukemias primarily following treatment with topoisomerase II inhibitors. We have studied five patients with a 3;21 translocation. In all cases, AML1 is interrupted after the runt domain, and is translocated to chromosome band 3q26. As a result of the t(3;21), AML1 is consistently fused to two separate genes located at 3q26. The two genes are EAP, which codes for the abundant ribosomal protein L22, and MDS1, which encodes a small polypeptide of unknown function. In one of our patients, a third gene EVI1 is also involved. EAP is the closest to the breakpoint junction with AML1, and EVI1 is the furthest away. The fusion of EAP to AML1 is not in frame, and leads to a protein that is terminated shortly after the fusion junction by introduction of a stop codon. The fusion of AML1 to MDS1 is in frame, and adds 127 codons to the interrupted AML1. Thus, in the five cases that we studied, the 3;21 translocation results in expression of two coexisting chimeric mRNAs which contain the identical runt domain at the 5' region, but differ in the 3' region. In addition, the chimeric transcript AML1/MDS1/EVI1 has also been detected in cells from one patient with the 3;21 translocation as well as in one of our patients. Several genes necessary for myeloid lineage differentiation contain the target sequence for AML1 in their regulatory regions. One of them is the CSF1R gene. We have compared the normal AML1 to AML1/MDS1, AML1/EAP and AML1/MDS1/EVI1 as transcriptional regulators of the CSF1R promoter. Our results indicate that AML1 can activate the promoter, and that the chimeric proteins compete with the normal AML1 and repress expression from the CSF1R promoter. AML1/MDS1 and AML1/EAP affect cell growth and phenotype when expressed in rat fibroblasts. However, the pattern of tumor growth of cells expressing the different chimeric genes in nude mice is different. We show that when either fusion gene is expressed, the cells lose contact inhibition and form foci over the monolayer. In addition, cells expressing AML1/MDS1 grow larger tumors in nude mice, whereas cells expressing only AML1/EAP do not form tumors, and cells expressing both chimeric genes induce tumors of intermediate size. Thus, although both chimeric genes have similar effects in transactivation assays of the CSF1R promoter, they affect cell growth differently in culture and have opposite effects as tumor promoters in vivo. Because of the results obtained with cells expressing one or both genes, we conclude that MDS1 seems to have tumorigenic properties, but that AML1/EAP seems to repress the oncogenic property of AML1/MDS1. PMID: 8585955 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 27: Oncogene. 1995 Sep 7;11(5):833-40. The AML1/Evi-1 fusion protein in the t(3;21) translocation exhibits transforming activity on Rat1 fibroblasts with dependence on the Evi-1 sequence. Kurokawa M, Ogawa S, Tanaka T, Mitani K, Yazaki Y, Witte ON, Hirai H. Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan. The t(3;21) (q26;q22) chromosomal translocation associated with blastic crisis of chronic myelogenous leukemia (CML) results in the formation of a chimeric protein fusing the amino-terminal DNA-binding domain encoded by the AML1 gene to the carboxyl-terminal-encoding portion of the Evi-1 gene. In order to evaluate transforming activity of this protein, AML1/Evi-1 was introduced into Rat1 fibroblasts. Cells expressing the fusion product formed macroscopic colonies in soft agar, indicating that AML1/Evi-1 is a transforming gene. It was also demonstrated that introduction of AML1/Evi-1 into the Rat1 clones harboring BCR/ABL also conferred enhanced capacity for anchorage independent growth. Analyses of deletion mutants of AML1/Evi-1 revealed that removal of the second zinc finger domain within the Evi-1 sequence totally abrogated the ability of AML1/Evi-1 to transform Rat1 cells. We showed that the transforming effect is correlated with the AP-1 activation induced by AML1/Evi-1. Furthermore, we demonstrated that c-jun is transcriptionally activated in Rat1 cells transformed by AML1/Evi-1, suggesting that c-jun expression is under control of AML1/Evi-1. These results indicate that the oncogenic effect of the t(3;21) translocation is caused by the generation of a chimeric transcriptional factor and that AML1/Evi-1 could perform a pivotal role in leukemic progression of CML. PMID: 7675444 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 28: Blood. 1995 Jul 1;86(1):1-14. AML1 and the 8;21 and 3;21 translocations in acute and chronic myeloid leukemia. Nucifora G, Rowley JD. Department of Medicine, University of Chicago, IL 60637, USA. Publication Types: Review PMID: 7795214 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 29: Mol Cell Biol. 1995 May;15(5):2383-92. Dual functions of the AML1/Evi-1 chimeric protein in the mechanism of leukemogenesis in t(3;21) leukemias. Tanaka T, Mitani K, Kurokawa M, Ogawa S, Tanaka K, Nishida J, Yazaki Y, Shibata Y, Hirai H. Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan. The chromosomal translocation t(3;21)(q26;q22), which is found in blastic crisis in chronic myelogenous leukemias and myelodysplastic syndrome-derived leukemias, produces AML1/Evi-1 chimeric transcription factor and is thought to play important roles in acute leukemic transformation of hemopoietic stem cells. We report here the functional analyses of AML1/Evi-1. It was revealed that AML1/Evi-1 itself does not alter the transactivation level through mouse polyomavirus enhancer-binding protein 2 (PEBP2; PEA2) sites (binding site of AML1) but dominantly suppresses the transactivation by intact AML1, which is assumed to be a stimulator of myeloid cell differentiation. DNA-binding competition is a putative mechanism of such dominant negative effects of AML1/Evi-1 because it binds to PEBP2 sites with higher affinity than AML1 does. Furthermore, AML1/Evi-1 stimulated c-fos promoter transactivation and increased AP-1 activity, as Evi-1 (which is not normally expressed in hemopoietic cells) did. Experiments using deletion mutants of AML1/Evi-1 showed that these two functions are mutually independent because the dominant negative effects on intact AML1 and the stimulation of AP-1 activity are dependent on the runt domain (DNA-binding domain of AML1) and the zinc finger domain near the C terminus, respectively. Furthermore, we showed that AML1/Evi-1 blocks granulocytic differentiation, otherwise induced by granulocyte colony-stimulating factor, of 32Dcl3 myeloid cells. It was also suggested that both AML1-derived and Evi-1-derived portions of the fusion protein play crucial roles in this differentiation block. We conclude that the leukemic cell transformation in t(3;21) leukemias is probably caused by these dual functions of AML1/Evi-1 chimeric protein. PMID: 7739522 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 30: Proc Natl Acad Sci U S A. 1994 Apr 26;91(9):4004-8. Consistent intergenic splicing and production of multiple transcripts between AML1 at 21q22 and unrelated genes at 3q26 in (3;21)(q26;q22) translocations. Nucifora G, Begy CR, Kobayashi H, Roulston D, Claxton D, Pedersen-Bjergaard J, Parganas E, Ihle JN, Rowley JD. Department of Medicine, University of Chicago, IL 60637. Two genes have been implicated in leukemias of patients with abnormalities of chromosome 3, band q26: EVI1, which can be activated over long distances by chromosomal rearrangements involving 3q26, and EAP, a ribosomal gene that fuses with AML1 in a therapy-related myelodysplasia patient with a t(3;21)(q26.2;q22). AML1 was identified by its involvement in the t(8;21)(q22;q22) of acute myeloid leukemia. Here we report the consistent identification of fusion transcripts between AML1 and EAP or between AML1 and previously unidentified sequences that we named MDS1 (MDS-associated sequences) in the leukemic cells of four patients with therapy-related myelodysplasia/acute myeloid leukemia and in one patient with chronic myelogenous leukemia in blast crisis, all of whom had a t(3;21). In addition, we have identified a third chimeric transcript, AML1/EVI1, in one of the therapy-related acute myeloid leukemia patients. Pulsed-field gel electrophoresis established the order of the genes as EAP, the most telomeric, and EVI1, the most centromeric, gene. The results indicate that translocations could involve multiple genes and affect gene expression over long distances. PMID: 8171026 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 31: EMBO J. 1994 Feb 1;13(3):504-10. Generation of the AML1-EVI-1 fusion gene in the t(3;21)(q26;q22) causes blastic crisis in chronic myelocytic leukemia. Mitani K, Ogawa S, Tanaka T, Miyoshi H, Kurokawa M, Mano H, Yazaki Y, Ohki M, Hirai H. Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan. The t(3;21)(q26;q22) translocation, which is one of the consistent chromosomal abnormalities found in blastic crisis of chronic myelocytic leukemia (CML), is thought to play an important role in the leukemic progression of CML to an acute blastic crisis phase. The AML1 gene, which is located at the translocation breakpoint of the t(8;21)(q22;q22) translocation found in acute myelocytic leukemia, was also rearranged by the t(3;21)(q26;q22) translocation. Screening of a cDNA library of the t(3;21)-carrying leukemic cell line cells (SKH1) resulted in the isolation of two potentially complete AML1-EVI-1 chimeric cDNAs of 6 kb. Two species of AML1-EVI-1 fusion transcripts of 8.2 and 7.0 kb were detected in SKH1 cells. These cells expressed the 180 kDa AML1-EVI-1 fusion protein containing an N-terminal half of AML1 including a runt homology domain which is fused to the entire zinc finger EVI-1 protein. The AML1-EVI-1 fusion transcript was consistent in all three cases of the t(3;21)-carrying leukemia examined by RNA-based PCR. These findings strongly suggest that the t(3;21) translocation results in the formation of a new class of chimeric transcription factor which could contribute to the leukemic progression of CML through interference with cell growth and differentiation. PMID: 8313895 [PubMed - indexed for MEDLINE] ---------------------------------------------------------------