E2F-Rb complexes assemble and inhibit cdc25A transcription in cervical carcinoma cells following repression of human papillomavirus oncogene expression.

Abstract	Expression of the bovine papillomavirus E2 protein in cervical carcinoma cells represses expression of integrated human papillomavirus (HPV) E6/E7 oncogenes, followed by repression of the cdc25A gene and other cellular genes required for cell cycle progression, resulting in dramatic growth arrest. To explore the mechanism of repression of cell cycle genes in cervical carcinoma cells following E6/E7 repression, we analyzed regulation of the cdc25A promoter, which contains two consensus E2F binding sites and a consensus E2 binding site. The wild-type E2 protein inhibited expression of a luciferase gene linked to the cdc25A promoter in HT-3 cervical carcinoma cells. Mutation of the distal E2F binding site in the cdc25A promoter abolished E2-induced repression, whereas mutation of the proximal E2F site or the E2 site had no effect. None of these mutations affected the activity of the promoter in the absence of E2 expression. Expression of the E2 protein also led to posttranscriptional increase in the level of E2F4, p105(Rb), and p130 and induced the formation of nuclear E2F4-p130 and E2F4-p105(Rb) complexes. This resulted in marked rearrangement of the protein complexes that formed at the distal E2F site in the cdc25A promoter, including the replacement of free E2F complexes with E2F4-p105(Rb) complexes. These experiments indicated that repression of E2F-responsive promoters following HPV E6/E7 repression was mediated by activation of the Rb tumor suppressor pathway and the assembly of repressing E2F4-Rb DNA binding complexes. Importantly, these experiments revealed that HPV-induced alterations in E2F transcription complexes that occur during cervical carcinogenesis are reversed by repression of HPV E6/E7 expression.
Authors	L Wu, E C Goodwin, L K Naeger, E Vigo, K Galaktionov, K Helin, D DiMaio
Journal	Molecular and cellular biology (Mol Cell Biol) Vol. 20 Issue 19 Pg. 7059-67 (Oct 2000) ISSN: 0270-7306 [Print] United States
PMID	10982822 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References	Carrier Proteins Cell Cycle Proteins DNA, Neoplasm DNA-Binding Proteins E2F Transcription Factors E2F4 Transcription Factor E2F4 protein, human Macromolecular Substances Multienzyme Complexes Neoplasm Proteins Phosphoproteins Proteins RBL2 protein, human Recombinant Fusion Proteins Retinoblastoma Protein Retinoblastoma-Binding Protein 1 Retinoblastoma-Like Protein p130 Transcription Factor DP1 Transcription Factors Viral Proteins CDC25A protein, human cdc25 Phosphatases Cysteine Endopeptidases Proteasome Endopeptidase Complex
Topics	Binding Sites Bovine papillomavirus 1 (genetics, physiology) Carcinoma, Squamous Cell (genetics, metabolism, pathology, virology) Carrier Proteins Cell Cycle (genetics, physiology) Cell Cycle Proteins Cell Transformation, Neoplastic (genetics) Cell Transformation, Viral (genetics) Consensus Sequence Cysteine Endopeptidases (metabolism) DNA, Neoplasm (genetics, metabolism) DNA-Binding Proteins (biosynthesis, genetics) E2F Transcription Factors E2F4 Transcription Factor Female Gene Expression Regulation, Neoplastic Gene Expression Regulation, Viral Genes, Retinoblastoma Humans Macromolecular Substances Multienzyme Complexes (metabolism) Neoplasm Proteins (genetics, metabolism) Papillomaviridae (genetics, physiology) Papillomavirus Infections (genetics, metabolism, pathology, virology) Phosphoproteins (biosynthesis, genetics) Promoter Regions, Genetic Proteasome Endopeptidase Complex Protein Binding Proteins Recombinant Fusion Proteins (biosynthesis, genetics) Retinoblastoma Protein (biosynthesis, genetics, metabolism) Retinoblastoma-Binding Protein 1 Retinoblastoma-Like Protein p130 Transcription Factor DP1 Transcription Factors (biosynthesis, genetics, metabolism) Transfection Tumor Cells, Cultured (metabolism) Tumor Virus Infections (genetics, metabolism, pathology, virology) Uterine Cervical Neoplasms (genetics, metabolism, pathology, virology) Viral Proteins (biosynthesis, genetics, physiology) cdc25 Phosphatases (biosynthesis, genetics)

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