ABSTRACT
As one of the immediate-early(IE)proteins of herpes simplex virus type 1(HSV-1),ICP22 is a multifunctional viral regulator that localizes in the nucleus of infected cells.It is required in experimental animal systems and some nonhuman cell lines,but not in Vero or HEp-2 cells.ICP22 is extensively phosphorylated by viral and cellular kinases and nucleotidylylated by casein kinase Ⅱ.It has been shown to be required for efficient expression of early(E)genes and a subset of late(L)genes.ICP22,in conjunction with the UL13 kinase,mediates the phosphorylation of RNA polymerase Ⅱ.Both ICP22 and UL13 are required for the activation of ode2,the degradation of cyclins A and B and the acquisition of a new cdc2 partner,the UL42 DNA polymerase processivity factor.The cdc2-UL42 complex mediates postranscriptional modification of topoisomerase Ⅱa in an ICP22-dependent manner to promote L gene expression.In addition,ICP22 interacts with cdk9 in a Us3 kinase dependent fashion to phosphorylate RNA polymerase Ⅱ.