Bromodomain protein 4 mediates the papillomavirus E2 transcriptional activation function.
The papillomavirus E2 regulatory protein has essential roles in viral transcription and the initiation of viral DNA replication as well as for viral genome maintenance. Brd4 has recently been identified as a major E2-interacting protein and, in the case of the bovine papillomavirus type 1, serves to tether E2 and the viral genomes to mitotic chromosomes in dividing cells, thus ensuring viral genome maintenance. We have explored the possibility that Brd4 is involved in other E2 functions. By analyzing the binding of Brd4 to a series of alanine-scanning substitution mutants of the human papillomavirus type 16 E2 N-terminal transactivation domain, we found that amino acids required for Brd4 binding were also required for transcriptional activation but not for viral DNA replication. Functional studies of cells expressing either the C-terminal domain of Brd4 that can bind E2 and compete its binding to Brd4 or short interfering RNA to knock down Brd4 protein levels revealed a role for Brd4 in the transcriptional activation function of E2 but not for its viral DNA replication function. Therefore, these studies establish a broader role for Brd4 in the papillomavirus life cycle than as the chromosome tether for E2 during mitosis.
Schweiger
Michal-Ruth
MR
Department of Pathology, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, USA.
You
Jianxin
J
Howley
Peter M
PM
D018797:Cell Cycle Proteins; D002460:Cell Line; D049109:Cell Proliferation; D004261:DNA Replication / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion / Q000235:genetics / Q000378:metabolism*; D009856:Oncogene Proteins, Viral / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D027383:Papillomaviridae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000235:genetics; D014157:Transcription Factors; D015533:Transcriptional Activation / Q000235:genetics*; D000092468:Bromodomain Containing Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D015514:Oncogene Proteins, Fusion; D009856:Oncogene Proteins, Viral; D034741:RNA, Small Interfering; D014157:Transcription Factors; C441289:BRD4 protein, human; D000092468:Bromodomain Containing Proteins; C054855:E2 protein, Human papillomavirus type 16