Upstream stimulating factor-1 (USF1) and USF2 bind to and activate the promoter of the adenomatous polyposis coli (APC) tumor suppressor gene.
The adenomatous polyposis coli (APC) gene product is involved in cell cycle arrest and apoptosis, and loss of function is associated with the development of colorectal carcinogenesis. Although it has been demonstrated that the APC gene is inducible, its transcriptional regulation has not been elucidated. Therefore, we characterized the promoter region of the APC gene and transcription factors required for basal expression. The APC gene has a TATA-less promoter and contains consensus binding sites for Octamer, AP2, Sp1, a CAAT-box, and three nucleotide sequences for E-box A, B, and M. The E-boxes are functional in several cancer cell lines and upstream stimulating factor-1 (USF1) and USF2 interact with these sites, with a preferred sequence-specificity for the B site. Analysis of activation of the cloned APC promoter by USF1 and USF2 in transient transfection assays in HCT-116 cells demonstrated that mutation of the E-box B site completely abolished the basal promoter activity. Further, the ectopic USF1 and USF2 expression in HCT-116 cells with deletion mutations of E-box A, B, and M sites showed that these E-boxes contribute to USF1- and USF2-mediated transcriptional activation of the APC promoter, with maximum promoter activity being associated with the E-box B site. Thus, USF1 and USF2 transcription factors are critical for APC gene expression.
Jaiswal
A S
AS
Department of Anatomy and Cell Biology, College of Medicine, University of Florida, Gainesville, Florida 32610, USA.
Narayan
S
S
D025601:Adenomatous Polyposis Coli Protein; D017209:Apoptosis; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D003001:Cloning, Molecular; D003110:Colonic Neoplasms / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics* / Q000378:metabolism*; D004268:DNA-Binding Proteins; D017353:Gene Deletion; D006801:Humans; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays; D051720:Upstream Stimulatory Factors
D025601:Adenomatous Polyposis Coli Protein; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D014157:Transcription Factors; C497181:USF1 protein, human; C497184:USF2 protein, human; D051720:Upstream Stimulatory Factors; D015500:Chloramphenicol O-Acetyltransferase