Gene UL2 of herpes simplex virus type 1 encodes a uracil-DNA glycosylase

An insertion mutant of herpes simplex virus type 1 has been constructed which carries the lacZ gene from Escherichia coli within the coding sequence of gene UL2, which is in the long unique region of the genome. In a one-step growth curve experiment this recombinant (called in 1601) grew as well as the wild-type (wt) parent virus, indicating that the UL2 gene is dispensable for growth in tissue culture. Analysis of in 1601 DNA with restriction endonucleases showed no detectable changes from the wt apart from the insertion. Extracts of cells infected with in 1601 possessed levels of viral DNA polymerase and alkaline exonuclease activities similar to those infected with the wt, but unlike the wt had negligible uracil-DNA glycosylase activity, suggesting strongly that the product of the UL2 gene is the uracil-DNA glycosylase. The sequence of the uracil-DNA glycosylase gene of E. coli was recently published, and the encoded amino acid sequence of this shows clear similarity to that of UL2, confirming our results.