Loading of Meiotic Cohesin by SCC-2 Is Required for Early Processing of DSBs and for the DNA Damage Checkpoint

SummaryBackgroundChromosome segregation and the repair of DNA double-strand breaks (DSBs) by homologous recombination require cohesin, the protein complex that mediates sister chromatid cohesion (SCC). In addition, cohesin is also required for the integrity of DNA damage checkpoints in somatic cells, where cohesin loading depends on a conserved complex containing the Scc2/Nipbl protein. Although cohesin is required for the completion of meiotic recombination, little is known about how cohesin promotes the repair of meiotic DSBs and about the factors that promote loading of cohesin during meiosis.ResultsHere we show that during Caenorhabditis elegans meiosis, loading of cohesin requires SCC-2, whereas the cohesin-related complexes condensin and SMC-5/6 can be loaded by mechanisms independent of both SCC-2 and cohesin. Although the lack of cohesin in scc-2 mutants impairs the repair of meiotic DSBs, surprisingly, the persistent DNA damage fails to trigger an apoptotic response of the conserved pachytene DNA damage checkpoint. Mutants carrying an scc-3 allele that abrogates loading of meiotic cohesin are also deficient in the apoptotic response of the pachytene checkpoint, and both scc-2 and scc-3 mutants fail to recruit the DNA damage sensor 9-1-1 complex onto persistent damage sites during meiosis. Furthermore, we show that meiotic cohesin is also required for the timely loading of the RAD-51 recombinase to irradiation-induced DSBs.ConclusionsWe propose that meiotic cohesin promotes DSB processing and recruitment of DNA damage checkpoint proteins, thus implicating cohesin in the earliest steps of the DNA damage response during meiosis.

► Cohesin is required for the apoptotic response to DNA damage during meiosis
► Meiotic cohesin is required for recruitment of the 9-1-1 complex to DNA damage sites
► Meiotic cohesin is required in the early stages of DSB processing
► Condensin and SMC-5/6 can be loaded independently of SCC-2 and cohesin