Activation of An Alternative, Rec12 (Spo11)-independent Pathway of Fission Yeast Meiotic Recombination in the Absence of a DNA Flap Endonuclease

Spo11 or a homologous protein appears to be essential for meiotic DNA double-strand break (DSB) formation and recombination in all organisms tested. We report here the first example of an alternative, mutationally -activated pathway for meiotic recombination in the absence of Rec12, the Spo11 homolog of Schizosaccharomyces pombe. Rad2, a FEN-1 flap endonuclease homolog, is involved in processing Okazaki fragments. In its absence, meiotic recombination and proper segregation of chromosomes were restored in rec12 mutants to nearly wild-type levels. Although readily detectable in wild-type strains, meiosis-specific DSBs were undetectable in recombination-proficient rad2 rec12 strains. Based on the biochemical properties of Rad2, we propose that meiotic recombination by this alternative (Rec*) pathway can be initiated by non-DSB lesions, such as nicks and gaps, that accumulate during premeiotic DNA replication in the absence of Okazaki fragment processing. We compare the Rec* pathway to alternative pathways of homologous recombination in other organisms.

Key Words: DNA flap endonuclease, Rad2 (Rad27), Rec12 (Spo11), Schizosaccharomyces pombe, meiotic recombination

Online ISS 1091-6490
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