The herpes simplex virus type 1 (HSV-1) UL37 open reading frame encodes a 120-kDa late (gamma 1) phosphoprotein in infected cells. Analysis of isolated mature HSV virions and light particles revealed that the UL37 protein is a component of the virion. Detergent solubilization and protease digestion experiments suggest that the UL37 protein is part of the tegument structure. Indirect immunofluorescence experiments using HSV-1-infected cells and cells infected with a vaccinia recombinant virus that expresses the UL37 gene demonstrated that the UL37 protein is present in both the nucleus and cytoplasm of infected cells and that localization to the nucleus does not require additional HSV proteins.

The UL37 and ICP8 proteins present in herpes simplex virus type 1 (HSV-1)-infected-cell extracts produced at 24 h postinfection coeluted from single-stranded-DNA-cellulose columns. Experiments carried out with the UL37 protein expressed by a vaccinia virus recombinant (V37) revealed that the UL37 protein did not exhibit DNA-binding activity in the absence of other HSV proteins. Analysis of extracts derived from cells coinfected with V37 and an ICP8-expressing vaccinia virus recombinant (V8) and analysis of extracts prepared from cells infected with the HSV-1 ICP8 deletion mutants d21 and nlO revealed that the retention of the UL37 protein on single-stranded DNA columns required a DNA-binding-competent ICP8 protein.

The herpes simplex virus type 1 (HSV-1) UL37 open reading frame encodes a 120-kDa late ('yl), nonstructural protein in infected cells. Recent studies in our laboratory have demonstrated that the UL37 protein interacts in the cytoplasm of infected cells with ICP8, the major HSV-1 DNA-binding protein. As a result of this interaction, the UL37 protein is transported to the nucleus and can be coeluted with ICP8 from single-stranded DNA columns. Pulse-labeling and pulse-chase studies of HSV-1-infected cells with [35S]methionine and 32p; demonstrated that UL37 was a phosphoprotein which did not have a detectable rate of turnover.