CHARACTERIZATION OF BOVINE HERPESVIRUS-1 UL49 HOMOLOG GENE AND PRODUCT - BOVINE HERPESVIRUS-1 UL49 HOMOLOG IS DISPENSABLE FOR VIRUS GROWTH

The sequence of the bovine herpesvirus 1 (BHV-1) gene that is homologo us to the herpes simplex virus UL49 gene was determined. The BHV-1 UL4 9 homolog open reading frame consists of 774 bp and is capable of enco ding 258 amino acids, Northern (RNA) blot analysis showed that the BHV -1 UL49 homolog is transcribed into a 1.1-kb RNA which is coterminal w ith the transcripts of an upstream UL49.5 homolog gene. Rabbit antiser a produced against synthetic peptides of the predicted UL49 homolog ge ne product recognized a polypeptide of 33 to 35 kDa in both virus-infe cted cells and isolated virions. Further analysis by unionic-detergent partition of isolated virions suggested that the UL49 homolog gene pr oduct is a virion tegument protein. Indirect immunofluorescence assay revealed that the UL49 homolog gene product was predominantly localize d in the nuclei of BHV-1-infected cells. A mutant virus with the UL49 homolog gene deleted was produced, and it was able to replicate in non complementing cells. Nevertheless, the yield of mutant virus was signi ficantly reduced. The results from this study suggest that the BHV-1 U L49 homolog gene encodes a nuclear protein which constitutes a tegumen t component in mature virions and that it is dispensable for virus gro wth in cell culture.