Multifunctional serine/threonine kinase that plays a role in several processes including egress of virus particles from the nucleus, modulation of the actin cytoskeleton and inhibition of apoptosis. Phosphorylates UL31 and UL34, two critical regulators of capsid budding from nucleus to endoplasmic reticulum, thereby facilitating virion egress. Modulates and redistributes host components of the nuclear envelope, including LMNA, emerin/EMD and the nuclear matrix protein MATR3. Phosphorylates envelope glycoprotein B (gB), probably to direct it to the cell surface. Promotes virus intracellular spread by restructuring host cell cytoskeleton. Blocks host apoptosis to extend cell survival and allow efficient viral replication. Promotes viral gene expression by phosphorylating host HDAC2 to reduce viral genome silencing (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Phosphorylated by protein 49; this phosphorylation regulates subsequent phosphorylation of proteins 27 and 29 by US3 homolog. Autophosphorylated (By similarity). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.