Regulatory mimicry of cyclin-dependent kinases by a conserved herpesvirus protein kinase

Herpesviruses encode conserved protein kinases (CHPKs) that target cellular cyclin-dependent kinase (CDK) phosphorylation sites; thus, they are termed viral CDK-like kinases. Tyrosine 15 in the GxGxxG motifs of CDK1 and CDK2, whose phosphorylation down-regulates their catalytic activities, is conserved in the corresponding motifs of CHPKs. We found that CHPK UL13, the corresponding Tyr-162 in herpes simplex virus 2 (HSV-2), was phosphorylated in HSV-2-infected cells. Mutational analyses of HSV-2 UL13 Tyr-162 suggested that phosphorylation of UL13 Tyr-162 reduced the phosphorylation of all UL13 substrates tested in HSV-2-infected cells. These findings suggested that HSV-2 UL13 mimicked the regulatory mechanism of CDKs and that this CHPK has regulatory and functional mimicry with CDKs. Furthermore, phosphorylation of HSV-2 UL13 Tyr-162 was suggested to be required for the downregulation of viral replication and pathogenicity, specifically in the brains of mice, and for efficient viral recurrence in guinea pigs. These findings highlight the dual impact of the regulatory mimicry of CDKs by CHPK on the fine-tuned regulation of lytic and latent HSV-2 infections in vivo.