Identification of proteins directly phosphorylated by UL13 protein kinase from herpes simplex virus 1.

Herpes simplex virus 1 (HSV-1) UL13 is a viral protein kinase that regulates optimal viral replication in cell cultures. Identification of substrates of protein kinases is a crucial step to elucidate the mechanism by which they function. Using our developed system to analyze the specific protein kinase activity of UL13, we have shown that UL13 protein kinase directly phosphorylates the viral proteins ICP22 and UL49 previously reported to be putative substrates. We also identified UL41 as a previously unreported and novel substrate of UL13. These data will serve as a basis to clarify the mechanism by which UL13 influences viral replication.