Abrogation of the Brd4-positive transcription elongation factor B complex by papillomavirus E2 protein contributes to viral oncogene repression.
The cellular bromodomain protein Brd4 is a major interacting partner of the papillomavirus (PV) E2 protein. Interaction of E2 with Brd4 contributes to viral episome maintenance. The E2-Brd4 interaction also plays an important role in repressing viral oncogene expression from the integrated viral genome in human PV (HPV)-positive cancer cells. However, the underlying mechanism is not clearly understood. In host cells, Brd4 recruits positive transcription elongation factor b (P-TEFb) to stimulate RNA polymerase II phosphorylation during cellular and viral gene expression. P-TEFb associates with the C terminus of Brd4, which largely overlaps with the E2 binding site on Brd4. In this study, we demonstrate that E2 binding to Brd4 inhibits the interaction of endogenous Brd4 and P-TEFb. P-TEFb is essential for viral oncogene E6/E7 transcription in both HeLa and CaSki cells that contain integrated HPV genomes. E2 binding to Brd4 abrogates the recruitment of P-TEFb to the integrated viral chromatin template, leading to inactivation of P-TEFb and repression of the viral oncogene E6/E7. Furthermore, dissociation of the Brd4-P-TEFb complex from the integrated viral chromatin template using a Brd4 bromodomain dominant-negative inhibitor also hampers HPV E6/E7 oncogene expression. Our data support that Brd4 recruitment of P-TEFb to the viral chromatin template is essential for viral oncogene expression. Abrogation of the interaction between P-TEFb and Brd4 thus provides a mechanism for E2-mediated repression of the viral oncogenes from the integrated viral genomes in cancer cells.
Yan
Junpeng
J
Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Li
Qing
Q
Lievens
Sam
S
Tavernier
Jan
J
You
Jianxin
J
D052685:Alphapapillomavirus / Q000235:genetics*; D018797:Cell Cycle Proteins; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000502:physiology*; D005814:Genes, Viral; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D009856:Oncogene Proteins, Viral / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000502:physiology; D027383:Papillomaviridae / Q000737:chemistry / Q000502:physiology*; D050725:Papillomavirus E7 Proteins; D042925:Positive Transcriptional Elongation Factor B / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D000092468:Bromodomain Containing Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D050725:Papillomavirus E7 Proteins; D042925:Positive Transcriptional Elongation Factor B; D012097:Repressor Proteins; D014157:Transcription Factors; C441289:BRD4 protein, human; D000092468:Bromodomain Containing Proteins; C054855:E2 protein, Human papillomavirus type 16; C068651:E6 protein, Human papillomavirus type 16; C059731:oncogene protein E7, Human papillomavirus type 16