Meiosis is a highly regulated process, partly due to the need to break and then repair DNA as part of the meiotic program. In this thesis, mechanisms of meiotic regulation are investigated, including the post-translational modification termed SUMOylation, and a potential novel negative regulator of error-prone DNA repair pathways. Post-translational modifications are widely used during meiotic events to regulate steps such as protein complex formation, checkpoint activation, and protein attenuation. In this thesis, we investigate how proteins that are obligatory components of the SUMO pathway, one such post-translational modification, affect the C. elegans germline. We show that UBC-9, the E2 conjugation enzyme, and the C. elegans homolog of SUMO, SMO-1, localized to germline nuclei throughout prophase I. Mutant analysis of smo-1 and ubc-9 revealed increased recombination intermediates throughout the germline, originating during the mitotic divisions. SUMOylation mutants also showed late meiotic defects including defects in the restructuring of oocyte bivalents and endomitotic oocytes (EMO). Increased rates of non-interfering crossovers (COs) were observed in ubc-9 heterozygotes, even though interfering COs were unaffected. We have also identified a physical interaction between UBC-9 and DNA repair protein MRE-11. ubc-9 and mre-11 null mutants exhibited similar phenotypes at germline mitotic nuclei and were synthetically sick. These phenotypes and genetic interactions were specific to MRE-11 null mutants as opposed to RAD-50 or resection-defective MRE-11. We propose that the SUMOylation pathway acts redundantly with MRE-11, and in this process MRE-11 likely plays a structural role.
We also found a candidate negative regulator of non-homologous end joining through an RNAi screen using the mre-11(iow1) resection-defective mutant. Mutant analysis did not rescue the resection-defective phenotype when multiple CRISPR-generated nhr-2 deletion alleles were generated. Therefore, nhr-2 does not appear to be directly involved in DNA repair.