CCAAT displacement protein binds to and negatively regulates human papillomavirus type 6 E6, E7, and E1 promoters.
Expression of human papillomavirus genes increases as the target cell, the keratinocyte, differentiates. CCAAT displacement protein (CDP) is a cellular protein which has been shown in other cell types to negatively regulate gene expression in undifferentiated cells but not in differentiated cells. We have previously shown that a 66-bp purine-thymidine-rich sequence (the 66-mer) binds CDP and negatively regulates the human papillomavirus type 6 (HPV-6) E6 promoter (S. Pattison, D. G. Skalnik, and A. Roman, J. Virol. 71:2013-2022, 1997). Cotransfection experiments with a plasmid expressing luciferase from the HPV-6 E6, E7, or E1 regulatory region and a plasmid carrying the CDP gene indicate that CDP represses transcription from all three HPV-6 promoters. Using electrophoretic mobility shift assays (EMSAs), we have shown that CDP binds HPV-6 both upstream and downstream of the E6, E7, and E1 transcription initiation start sites. Furthermore, when keratinocytes were induced to differentiate, all three promoter activities increased. Consistent with this, immunoblotting and EMSAs revealed that endogenous nucleus CDP and, correspondingly, DNA binding activity decreased when keratinocytes were induced to differentiate. The elevated promoter activities were abrogated by exogenously transfected CDP. Our data demonstrate that CDP fulfills the requirement of a differentiation-dependent negative regulator that could tie the HPV life cycle to keratinocyte differentiation.
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Department of Microbiology and Immunology, Indiana University School of Medicine, and Walther Cancer Institute, Indianapolis, Indiana 46202-5120, USA.
Toussaint
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Roman
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D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002454:Cell Differentiation; D002478:Cells, Cultured; D004279:DNA, Viral; D015967:Gene Expression Regulation, Viral; D018398:Homeodomain Proteins; D006801:Humans; D015603:Keratinocytes / Q000166:cytology; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D009856:Oncogene Proteins, Viral / Q000235:genetics*; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic
C080632:CUX1 protein, human; C000624101:Cux1 protein, mouse; D004279:DNA, Viral; C118861:E1 protein, Human papillomavirus type 6; C118860:E6 protein, Human papillomavirus type 6; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D014157:Transcription Factors; C062495:oncogene protein E7, Human papillomavirus type 6