title: Mutually exclusive interaction of the adenovirus E4-6/7 protein and the retinoblastoma gene product with internal domains of E2F-1 and DP-1.
abstract: The binding of E2F to the adenovirus (Ad) E2a promoter is stimulated by the Ad E4-6/7 protein. E2F DNA binding activity is composed of a heterodimer of related but distinct proteins of the E2F-1 and DP-1 families. The E4-6/7 protein induces the cooperative and stable binding of E2F to an inverted repeat binding site in the E2a promoter apparently by providing a dimerization interface to two adjacent E2F heterodimers. The product of the retinoblastoma gene product (Rb) represses the transcriptional activity of E2F by direct protein-protein interaction. In this report, we have examined the regions of E2F-1 and DP-1 that are required for the induction of cooperative E2F binding to the E2a promoter by the E4-6/7 protein. Our results demonstrate that an internal segment of E2F-1, that is conserved among members of the E2F family, is required for functional interaction with the E4-6/7 product. Consistent with this observation, other members of the E2F family (E2F-2 and E2F-3) productively interact with E4-6/7. DP-1 also is necessary for stable interaction with E4-6/7 and an internal segment of DP-1 is required that is positioned in a location similar to that of the conserved E2F-1 domain. Interestingly, the binding of E4-6/7 and the binding of Rb to E2F are mutually exclusive, and our results show that the same internal segments of E2F-1 and DP-1 that are required for E4-6/7 binding are also required for stable interaction with Rb. These results suggest that the Ad E4-6/7 protein mimics Rb in part for the protein interaction requirements for E2F binding, although with different functional consequences. While Rb binding represses E2F activity, the E4-6/7 protein stimulates transactivation of the Ad E2a promoter.
authors.affiliation: Department of Molecular Genetics and Microbiology, State University of New York, Stony Brook 11794.
authors.forename: R J
authors.initials: RJ
authors.lastname: O'Connor
authors.forename: P
authors.initials: P
authors.lastname: Hearing
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D017504:Adenovirus E4 Proteins / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050699:E2F3 Transcription Factor; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D016160:Retinoblastoma Protein / Q000378:metabolism*; D056465:Retinoblastoma-Binding Protein 1; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D017504:Adenovirus E4 Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050699:E2F3 Transcription Factor; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D014157:Transcription Factors; D004247:DNA