A novel plant gene essential for meiosis is related to the human CtIP and the yeast COM1/SAE2 gene

Abstract

Obligatory homologous recombination (HR) is required for chiasma formation and chromosome segregation in meiosis I. Meiotic HR is initiated by DNA double‐strand breaks (DSBs), generated by Spo11, a homologue of the archaebacterial topoisomerase subunit Top6A. In Saccharomyces cerevisiae, Rad50, Mre11 and Com1/Sae2 are essential to process an intermediate of the cleavage reaction consisting of Spo11 covalently linked to the 5′ termini of DNA. While Rad50 and Mre11 also confer genome stability to vegetative cells and are well conserved in evolution, Com1/Sae2 was believed to be fungal‐specific. Here, we identify COM1/SAE2 homologues in all eukaryotic kingdoms. Arabidopsis thaliana Com1/Sae2 mutants are sterile, accumulate AtSPO11‐1 during meiotic prophase and fail to form AtRAd51 foci despite the presence of unrepaired DSBs. Furthermore, DNA fragmentation in AtCom1 is suppressed by eliminating AtSPO11‐1. In addition, AtCOM1 is specifically required for mitomycin C resistance. Interestingly, we identified CtIP, an essential protein interacting with the DNA repair machinery, as the mammalian homologue of Com1/Sae2, with important implications for the molecular role of CtIP.

The MRE11 GAR motif regulates DNA double-strand break processing and ATR activation

“…The intrinsic activity of nuclease activities of MRE11 may be sufficient to promote fork degradation [47]. In conjunction with other factors, such as 5′-3′ exonucleases CtIP and EXO1, the MRN complex is functionally involved in the extensive degradation, leading to DNA end resection and homologous recombination [15,16,48,49]. Our findings suggest that the GAR motif may modulate the MRE11 exonuclease activity within the MRN complex in vivo, contributing to the defective ssDNA resection observed in Mre11 RK/RK MEFs (Figure 8).…”

Sae2p phosphorylation is crucial for cooperation with Mre11p for resection of DNA double-strand break ends during meiotic recombination in Saccharomyces cerevisiae

“…It is interesting that the C-terminal region of Sae2p, including the phosphorylation sites, has homology with human CtIP, fission yeast Ctp1, and novel proteins in plants and nematode (Limbo et al, 2007;Penkner et al, 2007;Sartori et al, 2007;Uanschou et al, 2007). Human CtIP interacts with the Mre11-Rad50-Nbs1 complex and BRCA1, which are associated with genetic disorders, and it functions in DSB resection (Yu et al, 2006;Sartori et al, 2007).…”

Processing of Meiotic DNA Double Strand Breaks Requires Cyclin-dependent Kinase and Multiple Nucleases

“…It has been shown that the sae2-S267A allele causes a strong reduction in spore viability (6,16) (Table 1). However, although both 3Ј-ended ssDNA and Spo11 removal were under the detection level in both sae2⌬ and sae2-S267A cells, spore viability was reduced to a lesser extent in sae2-S267A cells compared with sae2⌬ cells (Table 1).…”

“…Then, Spo11 must be removed by endonucleolytic cleavage to allow further DSB end processing by 5Ј-3Ј resection that is required to initiate homologous recombination (4). This event is promoted by the Sae2 protein and the MRX complex, which are required to catalyze the endonucleolytic removal of Spo11-linked oligonucleotides (3,5,6). In fact, budding yeast sae2⌬ cells and rad50s separation-of-function mutants allow DSB formation but are totally defective in Spo11 removal from DSB ends (3,5,(7)(8)(9).…”