Homologous recombination is required for the viability of rad27 mutants. Nucleic Acids Res

The RAD27/RTH1 gene of Saccharomyces cerevisiae encodes a structural and functional homolog of the 5′–3 ′ exonuclease function of Escherichia coli DNA polymerase I. Four alleles of RAD27 were recovered in a screen for hyper-recombination, a phenotype also displayed by polA mutants of E.coli. All four rad27 mutants showed similar high levels of mitotic recom-bination, but varied in their growth rate at various temperatures, and sensitivity to the DNA damaging agent methyl methane sulfonate. Dependence of viability of rad27 strains on recombination was deter-mined by crossing a strain containing a null allele of RAD27 to strains containing a mutation in either th