Deletion of UL21 causes a delay in the early stages of the herpes simplex virus 1 replication cycle

The herpes simplex virus 1 (HSV-1) U(L)21 gene encodes a 62-kDa tegument protein with homologs in the alpha-, beta-, and gammaherpesvirus subfamilies. In the present study, we characterized a novel U(L)21-null virus and its genetic repair to determine whether this protein plays a role in early stages of the HSV-1 replication cycle. Single-step growth analyses, protein synthesis time courses, and mRNA quantifications indicated that the absence of U(L)21 results in a delay early in the HSV-1 replication cycle.