The role of asymmetric protein dimethylation during the human papillomavirus lifecycle

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Infections with human papillomaviruses (HPVs) are the most common sexually transmitted infection in the US. In addition to causing cervical and other anogenital cancers and a rising incidence of head and neck cancer, HPVs are responsible for an estimated 5% of cancers worldwide. Importantly, persistent infection, and not an acute infection is the primary risk factor for (cervical) cancer development. Thus, understanding the virus-host interplay that promotes or restrict viral persistence has important implications for HPV biology and human cancers. Until recently, it has been challenging to study the immediate early events of the HPV lifecycle following infection and how these events contribute to initial genome amplification during the establishment phase and long-term viral persistence. We used a single-cell genomics approach to identify cellular factors involved in viral infection and persistence. Our preliminary data identify protein arginine N-methyltransferase 1 (PRMT1) as an important factor upon viral infection of primary human cervical cells. PRMT1 regulates several cellular functions that may be relevant to the HPV lifecycle. We demonstrate that PRMT1 inhibition leads to a highly dysregulated splicing pattern of the viral genes. Mechanistically, we identify a dramatic increase in m6A modifications of viral mRNA, specifically in introns. These data implicate RBM15, a regulatory subunit of the m6A methyltransferase complex. We hypothesize that PRMT1 regulates RBM15 controlled m6a deposition on viral mRNA to temporally regulate alternative splicing throughout viral infection. We will (1) Determine the importance of asymmetric protein dimethylation throughout the viral lifecycle. (2) Determine the role for RBM15 in the PRMT1 mediated regulation of m6a methylation of viral mRNA. (3) Determine the effects of m6a methylation on viral mRNA splicing. PRMT1 inhibition leads to dysregulated viral splicing. This proposal addresses a critical gap in our knowledge relating to how HPV splicing is regulated for optimal infection, establishment, and long-term persistence. We identify PRMT1 as a regulator of viral splicing and hypothesize that this occurs through targeted m6A deposition on viral introns. Since PRMT1 is an established druggable target, these results may lead to novel therapeutics for HPV-induced cancers.