The UL37 protein of herpes simplex virus type 1 is associated with the tegument of purified virions.

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.