Identification of three genes nonessential for growth in cell culture near the right terminus of the unique sequences of long component of herpes simplex virus 1.

We report the construction of herpes simplex virus 1 recombinants from which all or part of the coding sequences of four open reading frames have been deleted. In recombinants R7101 and R7108, the BamHI D' fragment containing the coding sequences of the dUTPase gene and the promoter-regulatory domain of a late gene was either replaced with a fragment containing a thymidine kinase gene or deleted, respectively. The recombinant R7107 lacks, in addition to BamHI D', 202 of a total of 244 predicted amino acids from the 3' end of the adjacent open reading frame UL51. The deletion in recombinant R7105 encompasses two genes, i.e., the entire open reading frame of UL47 and the amino terminus of UL46. These genes map next to that specifying the alpha trans-inducing factor. R7105, R7101, and R7108 do not exhibit demonstrable defects in viral replication. The recombinant R7107 forms minute plaques and replicates best in multiplying cells in subconfluent cultures. The results indicate that the multiplying cells supply at least some of the functions expressed by the protein encoded in UL51.