1: Oncogene. 2005 Jan 20;24(4):605-15. Interferons alpha and gamma induce p53-dependent and p53-independent apoptosis, respectively. Porta C, Hadj-Slimane R, Nejmeddine M, Pampin M, Tovey MG, Espert L, Alvarez S, Chelbi-Alix MK. UPR CNRS 9045, Institut Andre Lwoff, 7 rue Guy Moquet, 94801 Villejuif, France. Type I interferon (IFN) enhances the transcription of the tumor suppressor gene p53. To elucidate the molecular mechanism mediating IFN-induced apoptosis, we analysed programmed cell death in response to type I (IFNalpha) or type II (IFNgamma) treatment in relation to p53 status. In two cell lines (MCF-7, SKNSH), IFNalpha, but not IFNgamma, enhanced apoptosis in a p53-dependent manner. Furthermore, only IFNalpha upregulated p53 as well as p53 target genes (Noxa, Mdm2 and CD95). The apoptotic response to IFNalpha decreased in the presence of ZB4, an anti-CD95 antibody, suggesting that CD95 is involved in this process. When p53 was inactivated by the E6 viral protein or the expression of a p53 mutant, IFNalpha-induced apoptosis and p53 target genes upregulation were abrogated. Altogether these results demonstrate that p53 plays a pivotal role in the IFNalpha-induced apoptotic response. IFNalpha-induced PML was unable to recruit p53 into nuclear bodies and its downregulation by siRNA did not alter CD95 expression. In contrast, IFNgamma-induced apoptosis is p53-independent. CD95 and IFN-regulatory factor 1 (IRF1) are directly upregulated by this cytokine. Apoptotic response to IFNgamma is decreased in the presence of ZB4 and strongly diminished by IRF1 siRNA, implicating both CD95 and IRF1 in IFNgamma-induced apoptotic response. Taken together, these results show that in two different cell lines, IFNalpha and IFNgamma, induce p53-dependent -independent apoptosis, respectively. PMID: 15580300 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 2: Blood. 2004 Oct 15;104(8):2475-83. Epub 2004 Jun 24. Differential roles of STAT1alpha and STAT1beta in fludarabine-induced cell cycle arrest and apoptosis in human B cells. Baran-Marszak F, Feuillard J, Najjar I, Le Clorennec C, Bechet JM, Dusanter-Fourt I, Bornkamm GW, Raphael M, Fagard R. EA 3406 Universite Paris 13, Service de Biochimie, Hopital Avicenne, 125 route de Stalingrad, 93009 Bobigny Cedex, France. Signal transducer and activator of transcription 1 (STAT1), a transcription factor known to participate in antiviral responses, acts as a tumor suppressor inhibiting cell growth and promoting apoptosis. To study the role of STAT1 in DNA damage-induced apoptosis in B lymphocytes, its active form, STAT1alpha, was specifically inhibited by the overexpression of STAT1beta, the STAT1alpha truncated inhibitory isoform. An episomal vector with a tetracycline-inducible bidirectional promoter was created to induce the expression of 2 proteins, STAT1beta and enhanced green fluorescence protein (EGFP). The same vector was used to overexpress STAT1alpha as a control. Expression of STAT1beta inhibited the phosphorylation, the DNA-binding activity, and the transcriptional activity of STAT1alpha, as well as the expression of STAT1alpha target genes such as p21WAF1/CIP1, TAP1, IRF1, and PKR. Inhibiting STAT1alpha by STAT1beta increased the growth rate of transfected cells and their resistance to fludarabine-induced apoptosis and cell cycle arrest. Overexpressing STAT1beta reversed the negative regulation of Mdm2 expression observed after treatment with interferon-gamma (IFN-gamma), which activates STAT1, or with fludarabine. Nuclear translocation of p53 after fludarabine treatment was decreased when STAT1beta was overexpressed, and it was increased when STAT1alpha was induced. Oligonucleotide pull-down experiments showed a physical STAT1/p53 interaction. Our results show that imbalance between the antiproliferative/proapoptotic isoform STAT1alpha and the proliferative isoform STAT1beta is likely to play a crucial role in the regulation of proliferation and apoptosis and that STAT1alpha may regulate p53 activity and sensitize B cells to fludarabine-induced apoptosis. PMID: 15217838 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 3: J Biol Chem. 2003 Jul 18;278(29):26589-96. Epub 2003 May 5. The tumor suppressor interferon regulatory factor 1 interferes with SP1 activation to repress the human CDK2 promoter. Xie RL, Gupta S, Miele A, Shiffman D, Stein JL, Stein GS, van Wijnen AJ. Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA. Cell growth control by interferons (IFNs) involves up-regulation of the tumor suppressor interferon regulatory factor 1 (IRF1). To exert its anti-proliferative effects, this factor must ultimately control transcription of several key genes that regulate cell cycle progression. Here we show that the G1/S phase-related cyclin-dependent kinase 2 (CDK2) gene is a novel proliferation-related downstream target of IRF1. We find that IRF1, but not IRF2, IRF3, or IRF7, selectively represses CDK2 gene transcription in a dose- and time-dependent manner. We delineate the IRF1-responsive repressor element between nt -68 to -31 of the CDK2 promoter. For comparison, the tumor suppressor p53 represses CDK2 promoter activity independently of IRF1 through sequences upstream of nt -68, and the CDP/cut/Cux1 homeodomain protein represses transcription down-stream of -31. Thus, IRF1 repression represents one of three distinct mechanisms to attenuate CDK2 levels. The -68/-31 segment lacks a canonical IRF responsive element but contains a single SP1 binding site. Mutation of this element abrogates SP1-dependent enhancement of CDK2 promoter activity as expected but also abolishes IRF1-mediated repression. Forced elevation of SP1 levels increases endogenous CDK2 levels, whereas IRF1 reduces both endogenous SP1 and CDK2 protein levels. Hence, IRF1 represses CDK2 gene expression by interfering with SP1-dependent transcriptional activation. Our findings establish a causal series of events that functionally connect the anti-proliferative effects of interferons with the IRF1-dependent suppression of the CDK2 gene, which encodes a key regulator of the G1/S phase transition. PMID: 12732645 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 4: Mamm Genome. 2002 Jun;13(6):302-9. Detailed chromosomal and radiation hybrid mapping in the proximal part of rat Chromosome 10 and gene order comparison with mouse and human. Behboudi A, Roshani L, Kost-Alimova M, Sjostrand E, Montelius-Alatalo K, Rohme D, Klinga-Levan K, Stahl F. Department of Cell and Molecular Biology-Genetics, Lundberg Laboratory, Goteborg University, Box 462, Sweden. Afrouz.Behboudi@gen.gu.se The rat provides valuable and sometimes unique models of human complex diseases. To fully exploit the rat models in biomedical research, it is important to have access to detailed knowledge of the rat genome organization as well as its relation to the human genome. Rat Chromosome 10 (RNO10) harbors several important cancer-related genes. Deletions in the proximal part of RNO10 were repeatedly found in a rat model for endometrial cancer. To identify functional and positional candidate genes in the affected region, we used radiation hybrid (RH) mapping and single- and dual-color fluorescence in situ hybridization (FISH) techniques to construct a detailed chromosomal map of the proximal part of RNO10. The regional localization of 14 genes, most of them cancer-related ( Grin2a, Gspt1, Crebbp, Gfer, Tsc2, Tpsb1, Il9r, Il4, Irf1, Csf2, Sparc, Tp53, Thra1, Gh1), and of five microsatellite markers ( D10Mit10, D10Rat42, D10Rat50, D10Rat72, and D10Rat165) was determined on RNO10. For a fifteenth gene, Ppm1b, which had previously been assigned to RNO10, the map position was corrected to RNO6q12-q13. PMID: 12115033 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 5: Am J Hematol. 2001 Sep;68(1):23-31. Alterations in IRF1/IRF2 expression in acute myelogenous leukemia. Preisler HD, Perambakam S, Li B, Hsu WT, Venugopal P, Creech S, Sivaraman S, Tanaka N. Rush Cancer Institute, Rush Presbyterian St. Luke's Medical Center, Chicago, Illinois 60612, USA. hpreisler@rush.edu The interferon response genes 1 and 2 have been shown to be involved in the regulation of differentiation and proliferation of cells of the myeloid series, with the former functioning as an anti-oncogene and the latter as an oncogene. In the study described here, the levels of expression of these two genes and the ratio of their expression were compared in AML and normal marrow. The ratio of gene expression was significantly less in AML marrow cells as compared to normal marrow cells [med ratio = 1.33 vs. 2.97, P = 0.003]. While the expression ratio was unaffected by the presence or absence of either ras or fms mutations, p53 mutations were associated with higher IRF1:IRF2 expression ratios that wt p53 genes [med = 1.701 vs. 1.135, P = 0.014]. Given the functional characteristics and the competitive nature of these two genes, it is possible that leukemic transformation is associated with a fall in IRF1:IRF2 ratios. Finally, the administration of IL4 can result in the normalization of the IRF1:IRF2 ratio in the marrow cells of some patients with AML. Copyright 2001 Wiley-Liss, Inc. PMID: 11559933 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 6: Int J Radiat Biol. 2001 Jun;77(6):687-94. Comment in: Int J Radiat Biol. 2002 May;78(5):441-3. Int J Radiat Biol. 2002 May;78(5):443-5. Int J Radiat Biol. 2003 May;79(5):367-70; author reply 371-4. Microsatellite instability in acute myelocytic leukaemia developed from A-bomb survivors. Nakanishi M, Tanaka K, Takahashi T, Kyo T, Dohy H, Fujiwara M, Kamada N. Department of Cancer Cytogenetics, Research Institute for Radiation Biology and Medicine, Hiroshima University, Kasumi l-2-3, Minami-ku, Hiroshima 734-8553, Japan. PURPOSE: Genetic alterations, including microsatellite instability (MSI), are ultimate steps toward malignant process. To investigate MSI in A-bomb survivors, leukaemic cells were analysed from 13 acute myelocytic leukaemia patients with a history of radiation exposure and also in 12 de novo patients. MATERIALS AND METHODS: To assess the microsatellite changes, a fluorescent system in 10 loci (BAT40, D3S643, D5S107, IRF1, MYC, D9S171, WT1, TP53, DM, D17S855) was used. RESULTS: MSI analysis revealed a high frequency of multiple microsatellite changes in the exposed patients (84.6%) compared with non-exposed patients (8.3%). There was a significant difference (p < 0.001) between the two groups. CONCLUSIONS: These analyses clearly demonstrate that leukaemic cells from heavily exposed patients contain a number of genetic instabilities that may strongly influence the development of leukaemia among people exposed to the Hiroshima A-bomb radiation. PMID: 11403708 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 7: J Virol. 2001 Jul;75(13):6193-8. Viral interferon regulatory factor 1 of Kaposi's sarcoma-associated herpesvirus binds to p53 and represses p53-dependent transcription and apoptosis. Seo T, Park J, Lee D, Hwang SG, Choe J. Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea. Kaposi's sarcoma-associated herpesvirus (KSHV) is related to the development of Kaposi's sarcoma. Open reading frame K9 of KSHV encodes viral interferon regulatory factor 1 (vIRF1), which functions as a repressor of interferon- and IRF1-mediated signal transduction. In addition, vIRF1 acts as an oncogene to induce cellular transformation. Here we show that vIRF1 directly associates with the tumor suppressor p53 and represses its functions. The vIRF1 interaction domains of p53 are the DNA binding domain (amino acids [aa] 100 to 300) and the tetramerization domain (aa 300 to 393). p53 interacts with the central region (aa 152 to 360) of vIRF1. vIRF1 suppresses p53-dependent transcription and deregulates its apoptotic activity. These results suggest that vIRF1 may regulate cellular function by inhibiting p53. PMID: 11390621 [PubMed - indexed for MEDLINE] --------------------------------------------------------------- 8: J Biol Chem. 1997 Nov 21;272(47):29801-9. Identification of a novel transcriptional regulatory element common to the p53 and interferon regulatory factor 1 genes. Lallemand C, Bayat-Sarmadi M, Blanchard B, Tovey MG. Laboratory of Viral Oncology, CNRS, UPR 9045, IFC-1, 7, Rue Guy Moquet, 94801 Villejuif Cedex, France. The promoter regions of both the interferon regulatory factor (IRF1) and p53 antioncogenes contain a previously unidentified sequence denoted IRF1 p53 common sequence (IPCS), which markedly increases the transcriptional activity of a reporter gene placed under the control of an heterologous promoter in transfected U937 cells. In contrast, transfection of U937 cells with reporter vectors containing p53 and IRF1 promoters with mutated IPCS sites resulted in a 4-fold reduction in the constitutive expression of those two genes. The transcriptional activity of IPCS is strictly correlated with the binding of a novel nuclear factor, IPCS-binding factor (IPCS-BF). IPCS-BF, which is composed of a single polypeptide of 26 kDa, is present constitutively in nuclear extracts of both U937 cells and peripheral blood mononuclear cells from healthy donors. The finding that the pattern of binding of IPCS-BF to the IPCS is unlike that of any known transcription factor and that the IPCS sequence does not exhibit any significant homology with any known binding site present in the data base, strongly suggest that IPCS-BF is a novel transcription factor which, by virtue of this ability to regulate the expression of the p53 and IRF1 genes, could play a central role in the control of cell proliferation and/or apoptosis. PMID: 9368052 [PubMed - indexed for MEDLINE] ---------------------------------------------------------------