The pattern of sensitivity of yeast dna2 mutants to DNA damaging agents suggests a role in DSB and postreplication repair pathways

The Saccharomyces cerevisiae DNA2 gene encodes a DNA-stimulated ATPase and DNA helicase/nuclease essential for DNA replication. In characterizing dna2 mutants, we have found that Dna2p also participates in DNA repair or in da mage avoidance mechanisms, dna2 mutants are sensitive to X rays, although t hey are less sensitive than rad52 mutants. The X-ray sensitivity of dna2 mu tants is suppressed by overexpression of a 5' to 3' exonuclease, the yeast FEN-1 structure-specific nuclease, encoded by the RAD27 gene, which also su ppresses the growth defect of dna2-ts mutants. SGS1 encodes a helicase with similar properties to Dna2 protein. Although sgs1 Delta mutants are resist ant to X rays, dna2-2 sgs1 Delta double mutants are more sensitive to X ray s than the dna2-2 mutant. Temperature sensitive dna2 mutants are only sligh tly sensitive to UV light, show normal levels of spontaneous and UV induced mutagenesis, and have only a 2.5-fold elevated level of dinucleotide tract instability compared to wildtype. However, dna2 Delta strains kept alive b y overproduction of RAD27 are highly sensitive to UV light. These phenotype s, in addition to the epistasis analysis reported, allow us to propose that Dna2 is involved in postreplication and DSB repair pathways. (C) 2000 Publ ished by Elsevier Science B.V. All rights reserved.