Genes uvsX and uvsY of bacteriophage T4 both control genetic recombination and repair of damaged DNA, and their mutant phenotypes bear a striking resemblance to each other. It has been shown recently that the uvsX gene product is analogous to the recA gene product of Escherichia coli (Yonesaki et al. 1985; Yonesaki and Minagawa 1985; Formosa and Alberts 1986), but the function of the uvsY gene is unknown. To obtain further insight into the function of these genes we introduced plasmidborne copies of the two genes separately or together into E. coli. The uvsX gene rendered recA- cells more resistant to UV and raised the recombination frequency of lambda phage and E. coli, but hampered induction of the lambda prophage and the SOS function of E. coli. The uvsY gene had no detectable function when introduced alone into E. coli but significantly enhanced the function of the uvsX gene when the two plasmid-borne genes were introduced together.

We have previously shown that abnormally fast sedimenting DNA which accumulates upon infection of mutants of T4 phage defective in gene 49 is recombination intermediates, while the mutant gives rise to the recombination deficient phenotype, judging from genetic mating tests under the semipermissible condition (Minagawa and Ryo (1979) . To see the step to which the recombination process has proceeded in the DNA, we investigated by the transfection assay whether the generation of contiguous recombinant strands is completed.Such strands were found to be formed normally or nearly normally in the absence of the gene 49 function, supporting the view that the gene product is involved in resolution of branched recombinational intermediates into linear duplexes.

No abstract