Identification and characterization of the herpes simplex virus type 1 UL51 gene product

The products of the herpes simplex virus type 1 UL51 gene were identified as phosphoproteins with apparent molecular masses of 27, 29 and 30 kDa. The proteins were produced at the late stage of infection, in a manner highly dependent on viral DNA synthesis, and were associated with extra-cellular virions. Immunofluorescence studies local-ized the UL51 proteins mainly to the cytoplasm, both in infected Vero cells and in transfected COS-1 cells singly expressing the UL51 gene. Herpes simplex virus (HSV) is a large, enveloped DNA virus and the genome contains at least 84 different genes (Roizman et al., 1996). Approximately half of these genes have been shown to be dispensable for virus replication in cell cultures, but the proteins encoded by these dispensable genes are considered to play important roles in various aspects of virus growth and spread in the host. Although recent studies have identified most of the dispensable genes of HSV (Roizman & Sears, 1996; Roizman et al., 1996), the precise functions of many gene products remain obscure. The UL51 gene of HSV-1 is one of the dispensable genes that are located at the right end of the unique long (U L) region of the virus genome (Barker & Roizman, 1990; McGeoch et al., 1988) and its gene homologues are conserved throughout the herpesvirus famil