THE RAD18 GENE OF SCHIZOSACCHAROMYCES-POMBE DEFINES A NEW SUBGROUP OFTHE SMC SUPERFAMILY INVOLVED IN DNA-REPAIR

The rad18 mutant of Schizosaccharomyces pombe is very sensitive to kil ling by both UV and gamma radiation. We have cloned and sequenced the rad18 gene and isolated and sequenced its homolog from Saccharomyces c erevisiae, designated RHC18. The predicted Rad18 protein has all the s tructural properties characteristic of the SMC family of proteins, sug gesting a motor function-the first implicated in DNA repair. Gene dele tion shows that both rad13 and RHC18 are essential for proliferation. Genetic and biochemical analyses suggest that the product of the rad18 gene acts in a DNA repair pathway for removal of UV-induced DNA damag e that is distinct from classical nucleotide excision repair. This sec ond repair pathway involves the products of the rhp51 gene (the homolo g of the RAD51 gene of S. cerevisiae) and the rad2 gene.