Inhibition of human papillomavirus DNA replication by an E1-derived p80/UAF1-binding peptide

The papillomavirus E1 helicase is recruited by E2 to the viral origin, where it assembles into a double hexamer that orchestrates replication of the viral genome. We previously identified the cellular WD40 repeat-containing protein p80/UAF1 as a novel interaction partner of E1 from anogenital human papillomavirus (HPV) types. p80 was found to interact with the first 40 residues of HPV type 31 (HPV31) E1, and amino acid substitutions within this domain abrogated the maintenance of the viral episome in keratinocytes. In this study, we report that these p80-binding substitutions reduce by 70% the ability of E1 to support transient viral DNA replication without affecting its interaction with E2 and assembly at the origin in vivo. Microscopy studies revealed that p80 is relocalized from the cytoplasm to discrete subnuclear foci by E1 and E2. Chromatin immunoprecipitation assays further revealed that p80 is recruited to the viral origin in an E1- and E2-dependent manner. Interestingly, overexpression of a 40-amino-acid-long p80-binding peptide, derived from HPV31 E1, was found to inhibit viral DNA replication by preventing the recruitment of endogenous p80 to the origin. Mutant peptides defective for p80 interaction were not inhibitory, demonstrating the specificity of this effect. Characterization of this E1 peptide by nuclear magnetic resonance (NMR) showed that it is intrinsically disordered in solution, while mapping studies indicated that the WD repeats of p80 are required for E1 interaction. These results provide additional evidence for the requirement for p80 in anogenital HPV DNA replication and highlight the potential of E1-p80 interaction as a novel antiviral target.