The herpes simplex virus type 1 UL37 gene product is a component of virus particles

1 MRC Virology Unit, Institute of Virology, Church Street, Glasgow G11 5JR, U.K. and 2 International Agricultural College Larenstein, Marijkeweg 5, 6709 PE Wageningen, The Netherlands The herpes simplex virus type 1 UL37 gene encodes a protein with an M r of 120K that is produced at late times after infection. To study the properties of this protein we have linked a 10 amino acid epitope derived from a human cytomegalovirus protein to the UL37 polypeptide coding sequences by inserting an oligonucleotide at a Spe I site that is unique in the virus genome and lies close to the 3' end of the open reading frame. From studies on the resultant virus recombinant using a monoclonal antibody that recognizes the inserted epitope we find that, contrary to a previous report, the UL37 protein is a structural component of both virions and L particles and is present in the tegument of virus particles. Indirect immunofluorescence analysis revealed that the protein is distributed throughout infected cells but is more abundant in the cytoplasm than the nucleus. Received 5 January 1994; accepted 17 February 1994.