Pyk2 Regulates Human Papillomavirus Replication by Tyrosine Phosphorylation of the E2 Protein.

The human papillomavirus (HPV) E2 protein is a key regulator of viral transcription and replication. In this study, we demonstrate that the nonreceptor tyrosine kinase Pyk2 phosphorylates tyrosine 131 in the E2 transactivation domain. Both depletion of Pyk2 and treatment with a Pyk2 kinase inhibitor increased viral DNA content in keratinocytes that maintain viral episomes. The tyrosine-to-glutamic acid (E) mutant Y131E, which may mimic phosphotyrosine, failed to stimulate transient DNA replication, and genomes with this mutation were unable to establish stable episomes in keratinocytes. Using coimmunoprecipitation assays, we demonstrate that the Y131E is defective for binding to the C-terminal motif (CTM) of Bromodomain-containing protein 4 (Brd4). These data imply that HPV replication depends on E2 Y131 interaction with the pTEFb binding domain of Brd4.IMPORTANCE Human papillomaviruses are the major causative agents of cervical, oral, and anal cancers. The present study demonstrates that the Pyk2 tyrosine kinase phosphorylates E2 at tyrosine 131, interfering with genome replication. We provide evidence that phosphorylation of E2 prevents binding to the Brd4-CTM. Our findings add to the understanding of molecular pathways utilized by the virus during its vegetative life cycle and offers insights into the host-virus interactome.