A yeast replicative helicase, Dna2 helicase, interacts with yeast FEN-1 nuclease in carrying out its essential function

We have recently described a new helicase, the Dna2 helicase, that is essential for yeast DNA replication, We now show that the yeast FEN-1 (yFEN-1) nuclease interacts genetically and biochemically with Dna2 helicase. FEN-1 is implicated in DNA replication and repair in yeast, and the mammalian homolog of yFEN-1 (DNase TV, FEN-1, or MF1) participates in Okazaki fragment maturation, Overproduction of yFEN-1, encoded by RAD27/RTH1, suppresses the temperature-sensitive growth of dna2-1 mutants. Overproduction of Dnaa suppresses the rad27/rth1 Delta temperature-sensitive growth defect, dna2-1 rad27/rth1 Delta double mutants are inviable, indicating that the mutations are synthetically lethal, The genetic interactions are likely due to direct physical interaction between the two proteins, since both epitope-tagged yFEN-1 and endogenous SFEN-1 coimmuno-purify with tagged Dna2, The simplest interpretation of these data is that one of the roles of Dna2 helicase is associated with processing of Okazaki fragments.