Identification of interaction domains within the UL37 tegument protein of herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) UL37 is a 1123 amino acid tegument protein that self-associates and binds to the tegument protein UL36 (VP1/2). Studies were undertaken to identify regions of UL37 involved in these protein–protein interactions. Coimmunoprecipitation assays showed that residues within the carboxy-terminal half of UL37, amino acids 568–1123, are important for interaction with UL36. Coimmunoprecipitation assays also revealed that amino acids 1–300 and 568–1123 of UL37 are capable of self-association. UL37 appears to self-associate only under conditions when UL36 is not present or is present in low amounts, suggesting UL36 and UL37 may compete for binding. Transfection–infection experiments were performed to identify domains of UL37 that complement the UL37 deletion virus, K∆UL37. The carboxy-terminal region of UL37 (residues 568–1123) partially rescues the K∆UL37 infection. These results suggest the C-terminus of UL37 may contribute to its essential functional role within the virus-infected cell.