1: Biol Chem. 2001 Jun;382(6):891-902. 

Biological activity of mammalian transcriptional repressors.

Thiel G, Lietz M, Bach K, Guethlein L, Cibelli G.

Department of Medical Biochemistry and Molecular Biology, University of Saarland
Medical School, Homburg, Germany.

Research on the regulation of transcription in mammals has focused in recent
years mainly on the mechanism of transcriptional activation. However,
transcriptional repression mediated by repressor proteins is a common regulatory
mechanism in mammals and might play an important role in many biological
processes. To understand the molecular mechanism of transcriptional repression,
the activity of eight mammalian repressors or repressor domains was investigated
using a set of model promoters in combination with two different transcriptional
detection methods. The repressors studied were: REST, the thyroid hormone
receptors alpha and beta, the zinc finger protein NK10 containing a
'kruppel-associated box' (KRAB), repressor domains derived from the proteins
Egr-1, Oct2A and Dr1 and the repressor/activator protein YY1. Here we show that
the repressor domains of REST, Egr-1, the thyroid hormone receptors alpha< and
beta and NK10 were transferable to a heterologous DNA-binding domain and
repressed transcription from proximal and distal positions. Moreover, these
repressor domains also blocked the activity of a strong viral enhancer in a
'remote position'. Thus, these domains are 'general' transcriptional repressor
domains. The 'kruppel-associated box' was the most powerful repressor domain
tested. In contrast, the repressor domains derived from Oct2A and Dr1 were
inactive when fused to a heterologous DNA-binding domain. The repressor domain
of YY1 exhibited transcriptional repression activity only in one of the
transcriptional assay systems. The recruitment of histone deacetylases to the
proximity of the basal transcriptional apparatus was recently discussed as a
mechanism for some mammalian transcriptional repressor proteins. Here we show
here that histone deacetylase 2, targeted to the reporter gene via DNA-protein
interaction, functions as a transcriptional repressor protein regardless of the
location of its binding site within the transcription unit.

PMID: 11501753 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


2: J Immunol. 1996 Dec 15;157(12):5411-21. 

Cloning of the human platelet endothelial cell adhesion molecule-1 promoter and
its tissue-specific expression. Structural and functional characterization.

Almendro N, Bellon T, Rius C, Lastres P, Langa C, Corbi A, Bernabeu C.

Department of Immunology, Center of Biological Investigations, High Council of
Scientific Investigations, Madrid, Spain.

Platelet endothelial cell adhesion molecule-1 (PECAM-1; CD31) is a cell adhesion
molecule involved in transendothelial migration and expressed by hemopoietic and
endothelial cells. To understand the mechanisms underlying its regulated
expression, a genomic clone containing 1555 bp of the 5'-flanking region and the
first exon of the human PECAM-1 gene has been isolated. The 5'-flanking region
of the PECAM-1 gene lacks a consensus TATA box, but contains consensus motifs
for Sp1, EGR1, ets, helix-loop-helix (HLH) box, GATA, AP-2, C/EBP, YY1, CCACC,
LyF-1, imperfect octamer, heptamer, high mobility group proteins (HMG) box, and
nuclear factor-kappaB, as well as shear stress-, retinoic acid-,
glucocorticoid-, and acute phase-responsive elements, and an Alu sequence.
Successive 5' to 3' or 3' to 5' deletions revealed tissue-specific promoter
activity within the two contiguous 0.22-kb NheI/BglII and 0.44-kb BglII/PstI
fragments. The transcriptional activity displayed by the 0.22-kb NheI/BglII
fragment was specific for the myeloid lineage, whereas the promoter activity of
the 0.44-kb BglII/PstI fragment was apparently restricted to endothelial cells.
The transcriptional activity of the 0.22-kb NheI/BglII fragment was confirmed by
5' RACE (rapid amplification of 5' cDNA ends) and S1 nuclease protection
experiments that revealed previously unidentified transcription start sites. The
0.22-kb NheI/BglII promoter exhibited PMA inducibility in myeloid cells and
contained a PMA-responsive element recognized by Sp1 and EGR-1 transcription
factors. Isolation and characterization of the human PECAM-1 promoter represent
an initial step in elucidating the controlled expression of the PECAM-1 gene.

PMID: 8955189 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------