THE HSV-1 UL45 18 KDA GENE-PRODUCT IS A TRUE LATE PROTEIN AND A COMPONENT OF THE VIRION

Previously we constructed a null mutation in the HSV-1 UL45 gene, show ed that the UL45 gene was not required for growth in Vero cells, and c onfirmed that it coded for an 18 kDa protein (R.J. Visalli and C.R. Br andt, Virology 185:419-423, 1991). In this study, we have continued ou r characterization of the UL45 gene and the 18 kDa protein. Analysis o f UL45 RNA revealed that the gene was expressed late and was inhibited in the presence of phosphonoacetic acid (paa), indicating it is a gam ma2 class gene. Using a specific polyclonal antiserum, we found that t he 18 kDa UL45 gene product was also expressed late and was inhibited in the presence of paa. The 18 kDa protein was present in purified vir ions and was substantially enriched in the envelope-tegument fraction of virions disrupted with NP-40 detergent. The 18 kDa protein is thus a structural protein of the virus and appears to be associated with th e viral envelope. A 20 kDa protein that cross-reacted with a polyclona l HSV-1 UL45 antiserum was also detected in cells infected with HSV-2 strain 333.