The Lethal Phenotypes of Dna2 Mutations Are Rescued by Overexpression of the DNA Repair Proteins in Saccharomyces cerevisiae

초록

Dna2 protein involved in Okazaki fragment processing is a multifunctional enzyme with two essential enzyme activities, endonuclease and helicase. The endonuclease activity is essential to remove RNA-DNA primers of Okazaki fragments, while the helicase facilitates removal of secondary structures formed in the primers. In an effort to identify genes interacting genetically with DNA2, multi-copy suppressors were screened in yeast that rescue the lethality of Dna2 mutants devoid of helicase (dna2KE) or endonuclease (dna2DA) activities. A putative helicase, MPH1, was identified as a suppressor for dna2KE. Purified Mph1 protein possessed both ATPase and helicase activities, suggesting that it might replace the function of Dna2 helicase. The suppressors for dna2DA mutant encode the nucleases involved in the nucleotide excision or double-strand break repair pathways. They also contain several novel proteins that associate with these enzymes. These results suggest that some DNA repair proteins may participate in removing the unprocessed RNA-DNA primers which are not cleaved by Dna2 and/or other Okazaki fragment processing enzymes. [Supported by grant from KRF, KRF-2004-041-C00240]