title: The retinoblastoma susceptibility gene product represses transcription when directly bound to the promoter.
abstract: Rb represses E2F-mediated transcription in part by blocking the trans-activation domain of E2F. In addition, Rb can convert an E2F binding site from a positive to a negative element. To examine the effect of a Rb-DNA-bound complex on transcription, full-length Rb was fused to the DNA binding domain of GAL4. Here, we report that GAL4-Rb can repress transcription mediated by either Sp1, AP-1, or p53, dependent upon the presence of both the GAL4 DNA binding domain and GAL4 binding sites. Moreover, GAL4-Rb inhibited the activity of the herpes simplex virus tk promoter from GAL4 binding sites located at a distance from the promoter. In contrast, GAL4-Rb was unable to repress basal transcription. Cotransfection of specific cyclins and cyclin-dependent kinases or SV40 T-antigen abolished the repressive activity of GAL4-Rb. The domains of Rb involved in mediating the repression of transcription were mapped to regions that are overlapping, but not identical, to those required for the interaction with E2F. We propose that Rb can function as a general repressor of transcription when bound to the promoter region.
authors.affiliation: Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pennsylvania 15261, USA.
authors.forename: J
authors.initials: J
authors.lastname: Adnane
authors.forename: Z
authors.initials: Z
authors.lastname: Shao
authors.forename: P D
authors.initials: PD
authors.lastname: Robbins
mesh_terms: D000952:Antigens, Polyomavirus Transforming / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016160:Retinoblastoma Protein / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: D000952:Antigens, Polyomavirus Transforming; D016213:Cyclins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D009838:Oligodeoxyribonucleotides; D016160:Retinoblastoma Protein; D029701:Saccharomyces cerevisiae Proteins; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D016159:Tumor Suppressor Protein p53; D018844:Cyclin-Dependent Kinases