Comparative analysis of herpes simplex virus type 1 mutants that are defective in fusion function by using...

Mutants derived from herpes simplex virus type 1 (HSV-1) strains, YH and KOS, that were defective in cell fusion function (r mutants) were examined for DNA structure using a restriction endonuclease and gel electrophoresis. A distinct difference in the restriction patterns was found in some r mutants. One which was derived from strain YH and belonged to complementation group A lost the BamHI cleavage site in the long inverted repeat regions. But the site could not be associated with the gene that was related to the cell fusion event, inasmuch as the other mutants belonging to the same complementation group had a normal BamHI site. The others, which belonged to complementation group G of strain KOS, had a deletion of approximately 2 kb (kilobase-pair) in the BamHI B fragment. A mixed infection was carried out with r410 and r426 which belonged to groups A and G of strain KOS, respectively, and the viruses of parental and recombinant types were isolated from the progeny. The BamHI restriction fragment patterns of the DNAs showed that all recombinants, which carried the cell fusion ability, had the normal BamHI fragment B. Thus, one of the genes associated with cell fusion function must be located in BamHI fragment B.