Ctp1 CtIP and Rad32 Mre11 Nuclease Activity Are Required for Rec12 Spo11 Removal, but Rec12 Spo11 Removal Is Dispensable for Other MRN-Dependent Meiotic Functions

Abstract

ABSTRACT The evolutionarily conserved Mre11/Rad50/Nbs1 (MRN) complex is involved in various aspects of meiosis. Whereas available evidence suggests that the Mre11 nuclease activity might be responsible for Spo11 removal in Saccharomyces cerevisiae , this has not been confirmed experimentally. This study demonstrates for the first time that Mre11 ( Schizosaccharomyces pombe Rad32 Mre11 ) nuclease activity is required for the removal of Rec12 Spo11 . Furthermore, we show that the CtIP homologue Ctp1 is required for Rec12 Spo11 removal, confirming functional conservation between Ctp1 CtIP and the more distantly related Sae2 protein from Saccharomyces cerevisiae . Finally, we show that the MRN complex is required for meiotic recombination, chromatin remodeling at the ade6-M26 recombination hot spot, and formation of linear elements (which are the equivalent of the synaptonemal complex found in other eukaryotes) but that all of these functions are proficient in a rad50S mutant, which is deficient for Rec12 Spo11 removal. These observations suggest that the conserved role of the MRN complex in these meiotic functions is independent of Rec12 Spo11 removal.