Identification of AP-2 as an interactive target of Rb and a regulator of the G1/S control element of the hamster histone H3.2 promoter.
Previous studies have established that a 32 bp cis -regulatory region, referred to as the H3core spanning -241 to -210 of the hamster histone H3.2 promoter, is critical for its G1/S-phase induction of transcription. Here we report that the transcription factor AP-2 is a major component of the protein complex which interacts with the H3core from hamster nuclear extracts. In search of the control mechanism(s) whereby AP-2 can mediate cell cycle regulation of the histone H3.2 promoter, we found that AP-2 can physically interact with the retinoblastoma (Rb) tumor suppressor protein in vitro , and when over-expressed, can also associate with Rb in vivo . Importantly, in contrast to the majority of Rb binding proteins, the C-terminal domain of Rb alone is sufficient for its interaction with AP-2. Using a reporter gene system linking tandem copies of the H3core to a heterologous minimal promoter, we demonstrated that over-expression of AP-2 proteins results in transactivation of the reporter gene through the H3core in a sequence-specific but orientation-independent manner. Additionally, this stimulative effect was suppressed by co-expression of Rb. Thus, AP-2, through its physical and functional interaction with Rb, may contribute to the cell cycle regulation of its target genes.
Department of Biochemistry and Molecular Biology and the USC/Norris Comprehensive Cancer Center,University of Southern California School of Medicine, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA.
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D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D006224:Cricetinae; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D016193:G1 Phase / Q000235:genetics / Q000502:physiology; D017930:Genes, Reporter; D006657:Histones / Q000235:genetics*; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016160:Retinoblastoma Protein / Q000378:metabolism*; D016196:S Phase / Q000235:genetics / Q000502:physiology; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D006657:Histones; D016160:Retinoblastoma Protein; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D004247:DNA