Repression of the chicken c-rel promoter by vRel in chicken embryo fibroblasts is not mediated through a consensus NF-kappa B binding site.
To understand the regulation of expression of the chicken c-rel gene, we cloned genomic sequences upstream of the start site of transcription of c-rel. Sequence analysis shows that the c-rel promoter is a GC-rich promoter that lacks a TATA box. In addition, there are putative binding sites for several transcription factors, including an NF-kappa B consensus binding site. Primer extension showed that there is one major start site (site 1) for transcription in chicken embryo fibroblasts and two major start sites in a v-rel-transformed chicken spleen cell line. In transient assays using c-rel promoter sequences and the CAT reporter gene, we found that vRel repressed expression from the c-rel promoter. Other viral oncoproteins and a non-transforming v-rel deletion mutant did not repress the c-rel promoter. Repression occurred through sequences located within 125 bp of the start of transcription. However, mutation of the consensus NF-kappa B binding site did not affect the level of transcription from the c-rel promoter, nor did it interfere with repression by vRel, even though vRel could bind to the wild-type, but not the mutant, version of this sequence in vitro. These results suggest that the vRel protein can repress transcription through an indirect mechanism.
Capobianco
A J
AJ
Biology Department, Boston University, Massachusetts 02215.
Gilmore
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TD
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D005091:Exons; D007438:Introns; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D020569:Proto-Oncogene Proteins c-rel; D011519:Proto-Oncogenes; D014158:Transcription, Genetic
D016328:NF-kappa B; D009838:Oligodeoxyribonucleotides; D011518:Proto-Oncogene Proteins; D020569:Proto-Oncogene Proteins c-rel; D011505:Protein-Tyrosine Kinases