title: Phosphorylation of HPV-16 E2 at serine 243 enables binding to Brd4 and mitotic chromosomes.
abstract: The papillomavirus E2 protein is involved in the maintenance of persistent infection and known to bind either to cellular factors or directly to mitotic chromosomes in order to partition the viral genome into the daughter cells. However, how the HPV-16 E2 protein acts to facilitate partitioning of the viral genome remains unclear. In this study, we found that serine 243 of HPV-16 E2, located in the hinge region, is crucial for chromosome binding during mitosis. Bromodomain protein 4 (Brd4) has been identified as a cellular binding target through which the E2 protein of bovine papillomavirus type 1 (BPV-1) tethers the viral genome to mitotic chromosomes. Mutation analysis showed that, when the residue serine 243 was substituted by glutamic acid or aspartic acid, whose negative charges mimic the effect of constitutive phosphorylation, the protein still can interact with Brd4 and colocalize with Brd4 in condensed metaphase and anaphase chromosomes. However, substitution by the polar uncharged residues asparagine or glutamine abrogated Brd4 and mitotic chromosome binding. Moreover, following treatment with the inhibitor JQ1 to release Brd4 from the chromosomes, Brd4 and E2 formed punctate foci separate from the chromosomes, further supporting the hypothesis that the association of the HPV-16 E2 protein with the chromosomes is Brd4-dependent. In addition, the S243A E2 protein has a shorter half-life than the wild type, indicating that phosphorylation of the HPV-16 E2 protein at serine 243 also increases its half-life. Thus, phosphorylation of serine 243 in the hinge region of HPV-16 E2 is essential for interaction with Brd4 and required for host chromosome binding.
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Szu-Wei
authors.initials: SW
authors.lastname: Chang
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Wei-Chen
authors.initials: WC
authors.lastname: Liu
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Kuan-Yu
authors.initials: KY
authors.lastname: Liao
authors.affiliation: Department of Ophthalmology, Mackay Memorial Hospital, Taipei, Taiwan.
authors.forename: Yeou-Ping
authors.initials: YP
authors.lastname: Tsao
authors.affiliation: Department of Bioscience and Biotechnology, College of Life Sciences, National Taiwan Ocean University, Keelung, Taiwan.
authors.forename: Pang-Hung
authors.initials: PH
authors.lastname: Hsu
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Show-Li
authors.initials: SL
authors.lastname: Chen
mesh_terms: D000705:Anaphase; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D019556:COS Cells; D018797:Cell Cycle Proteins; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000737:chemistry*; D016679:Genome, Viral; D018698:Glutamic Acid / Q000737:chemistry; D005973:Glutamine / Q000737:chemistry; D057809:HEK293 Cells; D052162:Human papillomavirus 16 / Q000235:genetics*; D006801:Humans; D008677:Metaphase; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D009856:Oncogene Proteins, Viral / Q000737:chemistry*; D010641:Phenotype; D010766:Phosphorylation; D011485:Protein Binding; D012694:Serine / Q000737:chemistry*; D014157:Transcription Factors / Q000378:metabolism*; D000092468:Bromodomain Containing Proteins
chemical_list: D001224:Aspartic Acid; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D018698:Glutamic Acid; D005973:Glutamine; D009687:Nuclear Proteins; D009856:Oncogene Proteins, Viral; D012694:Serine; D014157:Transcription Factors; C441289:BRD4 protein, human; D000092468:Bromodomain Containing Proteins; C054855:E2 protein, Human papillomavirus type 16