Serine/threonine protein kinase that plays important roles in several processes including nuclear viral egress, viral replication or regulation of host cell cycle progression. Participates in the acquisition of tegument during virion morphogenesis in the nucleus. Redistributes the host nuclear lamina by phosphorylating cellular Lamins-A/C. Plays a role in viral DNA synthesis by phosphorylating the DNA polymerase processivity factor UL44. Stimulates host cell cycle to support viral DNA synthesis by phosphorylating host retinoblastoma/RB1 protein. Additional substrates have been identified including host EF1D or H2B. Phosphorylates also host SAMHD1 and thereby counteracts its antiviral effect by reducing its dNTP hydrolase activity. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with UL83. Autophosphorylates on serine and threonine residues. Belongs to the protein kinase superfamily. Tyr protein kinase family. HCMV ganciclovir subfamily.