Resolution of genotypic and phenotypic properties of herpes simplex virus type 1 temperature-sensitive mutant (KOS) tsZ47: evidence for allelic complementation in the UL28 gene.

Herpes simplex virus type 1 (HSV-1) mutant tsZ47 was reported to be temperature sensitive for virus growth and transport of viral glycoproteins to the cell surface and to contain two different mutations (B. A. Pancake, D. P. Aschman, and P. A. Schaffer, (1983) J. Virol. 47,568-585). However, we found that similar amounts of glycoproteins B, C and H were expressed at the cell surface at the permissive and non-permissive temperatures and in addition, tsZ47 virus contained only a single mutation. UL28-null virus, gC delta 7B, failed to complement tsZ47 in mixed infections and tsZ47 replicated in UL28 but not gB transformed cell lines. A ts lesion of tsZ47 was mapped within a 1333 bp region of the UL28 gene by marker-rescue using overlapping DNA fragments. DNA sequencing identified a C to T transversion resulting in an R to W amino acid change at UL28 amino acid position 531. Southern Blot analysis and transmission electron microscopy demonstrated that tsZ47, is defective in cleavage and encapsidation of viral DNA. Mutant virus ts1203 (C. Addison, F.J. Rixon, and V.G. Preston, (1990) J. Gen. Virol. 71, 2377-2384) that contains a mutation in the 5' end of UL28, complemented tsZ47 in mixed infections. This suggests that allelic complementation may be occurring and UL28 may encode a protein with independently functioning domains, or that it participates in a multimer.