Cloning and characterization of the human BAG-1 gene promoter: upregulation by tumor-derived p53 mutants.
BAG-1 is an anti-apoptotic protein that interacts with Bcl-2, Bcl-XL, Hsp70/Hsc70, Raf-1 and numerous hormone or growth factor receptors. Recently, BAG-1 has been found to be overexpressed in a variety of human cancer cell lines and some tumors. However, the molecular mechanism of BAG-1 upregulation is still unclear. In this study, we cloned 0.9 kb of human genomic DNA, BGEV, 5' flanking the BAG-1 open reading frame. BGEV subcloned into a promoterless luciferase reporter vector conferred high promoter activity in various human cancer cell lines. Deletion analysis of this sequence localized the region of maximal BAG-1 promoter activity from nucleotide positions -353 to -54, upstream of the first start codon CTG. Sequence analysis of the BAG-1 promoter region showed the absence of a TATA box but identified a CCAAT box, several GC boxes, a CpG island and several transcriptional factor binding sites, which may be important in the regulation of BAG-1 transcription. Most importantly, functional characterization of the BAG-1 promoter in vivo demonstrated that gain-of-function p53 mutants derived from human tumors upregulated the transcription of BAG-1 RNA and the expression of a reporter gene from the BAG-1 promoter. These results indicated that we have isolated the functional constitutive BAG-1 promoter. Furthermore, the data suggested that overexpression of BAG-1 in some tumors may be due to upregulation of the human BAG-1 promoter by mutant p53.
Yang
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Division of Basic Medical Sciences, Faculty of Medicine, Memorial University of Newfoundland, 300 Prince Philip Drive, St John's, Newfoundland, Canada, A1B 3V6.
Pater
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Tang
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D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D014157:Transcription Factors; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D015854:Up-Regulation
C091732:BCL2-associated athanogene 1 protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53