MUTATIONS IN SACCHAROMYCES-CEREVISIAE THAT BLOCK MEIOTIC PROPHASE CHROMOSOME METABOLISM AND CONFER CELL-CYCLE ARREST AT PACHYTENE IDENTIFY 2 NEW MEIOSIS-SPECIFIC GENES SAE1 AND SAE3

Two new meiosis-specific genes, SAE1 and SAE3 have been identified in a screen for mutations that confer an intermediate block in meiotic pr ophase. Such mutations confer a block to spore formation that is circu mvented by addition of a mutation that eliminates meiotic recombinatio n initiation and other aspects of chromosome metabolism, i.e., spo11. We show that sae1-1 and sae3-1 mutations each confer a distinct defect in meiotic recombination. sae1-1 produces recombinants but very slowl y and ultimately to less than half the wild-type level; sae3-1 makes p ersistent hyper-resected meiotic double-strand breaks and has a severe defect in formation of recombinants. Both mutants arrest at the pachy tene stage of meiotic prophase, sae1-1 temporarily and sae3-1 permanen tly. The phenotypes conferred by sae3-1 are similar to those conferred by mutation of the yeast RecA homologue DMC1, suggesting that SAE3 an d DMC1 act at the same step(s) of chromosome metabolism. These results provide further evidence that intermediate blocks to prophase chromos ome metabolism cause cell-cycle arrest. SAE1 encodes a 208-residue pro tein homologous to vertebrate mRNA cap-binding protein 20. SAE3 corres ponds to a meiosis-specific RNA encoding an unusually short open readi ng frame of 50 codons.