Herpes Simplex Virus 1 ICP22 Regulates the Accumulation of a Shorter mRNA and of a Truncated U S 3 Protein Kinase That Exhibits Altered Functions

Abstract

ABSTRACT The U S 3 open reading frame of herpes simplex virus 1 (HSV-1) was reported to encode two mRNAs each directing the synthesis of the same protein. We report that the U S 3 gene encodes two proteins. The predominant U S 3 protein is made in wild-type HSV-1-infected cells. The truncated mRNA and a truncated protein designated U S 3.5 and initiating from methionine 77 were preeminent in cells infected with a mutant lacking the gene encoding ICP22. Both the wild-type and truncated proteins also accumulated in cells transduced with a baculovirus carrying the entire U S 3 open reading frame. The U S 3.5 protein accumulating in cells infected with the mutant lacking the gene encoding ICP22 mediated the phosphorylation of histone deacetylase 1, a function of U S 3 protein, but failed to block apoptosis of the infected cells. The U S 3.5 and U S 3 proteins differ with respect to the range of functions they exhibit.