FUNCTIONAL DOMAINS WITHIN FEN-1 AND RAD2 DEFINE A FAMILY OF STRUCTURE-SPECIFIC ENDONUCLEASES - IMPLICATIONS FOR NUCLEOTIDE EXCISION-REPAIR

Structure-specific nucleases catalyze critical reactions in DNA replic ation, recombination, and repair. Recently, a structure-specific endon uclease, FEN-1, has been purified and shown to cleave DNA flap structu res. Here, we describe the cloning of the murine FEN-1 gene. The nucle otide sequence of FEN-1 is highly homologous to the Saccharomyces cere visiae genes YKL510 and RAD2. We show that YKLS10 and a truncated RAD2 protein are also structure-specific endonucleases. The substrate spec ificity of the truncated RAD2 protein implicates branched DNA structur es as important intermediates in nucleotide excision repair. The polar ity of these branched DNA structures allows us to predict the placemen t of DNA scissions by RAD2 and RAD1/RAD10 in this reaction.