Novel function of Rad27 (FEN-1) in restricting short-sequence recombination

Saccharomyces cerevisiae mutants lacking the structure-specific nuclease Ra d27 display an enhancement in recombination that increases as sequence leng th decreases, suggesting that Rad27 preferentially restricts recombination between short sequences. Since wild-type alleles of both RAD27 and its huma n homologue FEN1 complement the elevated short-sequence recombination (SSR) phenotype of a rad27-null mutant, this function may be conserved from yeas t to humans. Furthermore, mutant Rad27 and FEN-1 enzymes,vith partial flap endonuclease activity but without nick specific exonuclease activity partia lly complement the SSR phenotype of the rad27-null mutant. This suggests th at the endonuclease activity of Rad27 (FEN-1) plays a role in limiting reco mbination between short sequences in eukaryotic cells.