Identification of Novel F-Box Proteins that Regulate Caenorhabditis elegans Synapsis

Meiosis is a specialized type of cell division that lays the foundation of propagation for all sexually reproducing lifeforms. During meiotic prophase, a proteinaceous structure called the synaptonemal complex (SC) assembles between paired homologous chromosomes via a process known as synapsis. The SC is a crucial structure that stabilizes the pairwise interaction of homologs and prevents their dissociation, which in turn allows for proper chromosomal segregation during the meiotic division cycle. In recent years, the Skp1-Cullin 1-F-box protein (SCF) complex has emerged as an essential regulator of synapsis across diverse eukaryotes. Yet, exactly how the SCF complex regulates aspects of synapsis remains unknown. Here, we identify two Skp1-related (skr) genes, skr-1 and skr-2, as paralogs that have arisen from a local duplication event in the nematode, Caenorhabditis elegans. Importantly, this duplication appears to have been exclusive to C. elegans across the Caenorhabditis genus. Reverse genetic screening by RNAi also implicate the role of F-box proteins in synapsis. Preliminary analysis of the F-box protein, LIN-23, demonstrates its involvement in SC disassembly. Interestingly, however, RNAi knockdown of CUL-1, the core scaffolding component of the SCF complex, has no impact on SC structure. Taken together, regulation of the SC in C. elegans may be occurring both outside and within the context of the SCF complex: Skp1 proteins and F-box proteins function SCF-independently to assemble the SC but perform SCF-dependent roles for SC disassembly. C. elegans, therefore, seems to share the evolutionarily conserved involvement of the SCF complex in SC regulation but may have further extended Skp1’s canonical role as an SCF component to a more self-contained modulator of the SC