Interaction of human cytomegalovirus pUL84 with casein kinase 2 is required for oriLyt-dependent DNA replication.

Human cytomegalovirus pUL84 is a phosphorylated protein that is required for lytic DNA replication and participates in regulation of virus gene expression. We previously used a proteomics assay to show that human cytomegalovirus pUL84 interacts with casein kinase 2 (CK2). We now have demonstrated that pUL84 is a substrate for CK2 in vitro, and we have determined that two putative CK2 phosphorylation sites within pUL84 mediate binding to CK2. Mutation of a threonine residue at amino acid (aa) 148 and a serine residue at aa 157 within the pUL84 protein resulted in the inability of the protein to interact with the CK2alpha subunit in transfected cells. Interaction of pUL84 with CK2 was essential for complementation of oriLyt-dependent DNA replication, suggesting that phosphorylation is an essential modification.