Meiosis is the specialized cellular division that starts from a diploid meiocyte leading to the formation of 4 haploid gametes. The first meiotic division uses DNA damage repair to pair homologous chromosomes for proper segregation. Once paired, the Synaptonemal Complex (SC), a tripartite proteinaceous structure, assembles along homologous chromosomes to provide pairing stabilization. Stabilization allows for recombination to fix the DNA damage and create crossovers between homologs. The SC disassembles leaving the crossover holding together homologs up to their segregation. Previously, our lab has shown that the CSN/COP-9 complex plays a crucial role in SC assembly. CSN/COP-9 has deneddylation activity which is specific to Cullin E3 ligases. E3 ligases are activated by the addition of NED-8 and deactivated by the release of NED-8. Mutants of the complex, as well as NED-8 knockdown, lead to SC polycomplex formation. Due to uncompleted synapsis, DNA damage accumulates in these nuclei leading to a decrease in overall crossovers. We have previously shown that the CUL-4 E3 ligase is the likely target of CSN/COP-9, but further investigation of the CUL-4 complex was lacking. Here we show that the CUL-4 complex plays a role in both SC assembly and DNA damage repair. Mutants of the CUL-4 complex have SC polycomplex formation throughout pachytene. These mutants also have defects in DNA damage repair as RAD-51 immunofluorescent staining shows high levels within nuclei. We also show that not all canonical components of the CUL-4 complex are required for SC assembly. Through SYP-1 immunofluorescent staining, we found that DDB-1, a protein that connects CUL-4 to an adapter protein, and GAD-1, the adapter protein, are both involved in SC assembly. Interestingly, the RING proteins, RBX-1 and RBX-2, docking sites for E2 conjugating enzymes, are not required for SC assembly. During Cullin E3 ligase cycling, CAND-1 binding prevents reactivation until it's released which allows for reactivation. We found that loss of CAND-1 had no effect on SC assembly, suggesting that cycling but not sequestering of the inactive complex is necessary for SC assembly. The function of the Cullin E3 ligases are to ubiquitinate targeted proteins either for degradation or other functions such as signaling. We show that in
csn-5 mutants, there is an increase in the localization of LYS-48 ubiquitination to nuclei, the residue associated with degradation. Whereas in
cul-4 mutants, there is a lower nuclear signal of LYS-48 as compared to
csn-5 mutants. This suggests that over-ubiquitination of target proteins or over-self-ubiquitination of CUL-4 is occurring in these mutants. Altogether, we suggest that the CUL-4 E3 ligase complex functions in both SC assembly and DNA damage repair through its ubiquitination activity.