A MEIOTIC RECOMBINATION CHECKPOINT CONTROLLED BY MITOTIC CHECKPOINT GENES

IN budding yeast, meiotic recombination occurs at about 200 sites per cell and involves DNA double-strand break (DSB) intermediates(1-3). He re we provide evidence that a checkpoint control requiring the mitotic DNA-damage checkpoint genes RAD17, RAD24 and MEC1 ensures that meioti c recombination is complete before the first meiotic division (MI). Fi rst, RAD17, RAD24 and MEC1 are required for the meiotic arrest caused by blocking the repair of DSBs with a mutation in the recA homologue D MC1. Second, mec1 and rad24 single mutants (DMC1(+)) appear to undergo MI before all recombination events are complete. Curiously, the mitos is-specific checkpoint gene RAD9 is not required for meiotic arrest of dmc1 mutants(4), This shows that although mitotic and meiotic control mechanisms are related, they differ significantly, Rad17 and Rad24 pr oteins may contribute directly to formation of an arrest signal by ass ociation with single-strand DNA in mitosis and meiosis.