Determining the mechanism of CSR-1 RNAi pathway to organize holocentromere in Caenorhabditis elegans

Abstract

CSR-1 RNAi pathway is required for the holocentromere organization and proper chromosome segregation in Caenorhabditis elegans. It remains obscure how this pathway functionally links to these two events. A previous study showed that germline genes, which are targets of CSR-1 RNAi pathway, are inversely correlated to the centromeric histone H3 protein variant, HCP-3, occupancy on chromatin. We propose that CSR-1 RNAi pathway may restrict HCP-3 localization on the centromere. To study how the CSR-1 RNAi pathway affects the centromere function, we have closely examined the centromeric protein localization following RNAi knockdown of the Argonaute csr-1. Our live imaging data shows that csr-1 knockdown does not affect the bipolar arrangement of HCP-3 on centromere but elevates the centromeric HCP-3 level. We propose that the increase in HCP-3 chromatin localization results in merotelic kinetochore attachment and thus leads to chromosome missegregation. We will determine if tethering CSR-1 onto an HCP-3-enriched region will reduce HCP-3 occupancy by ChIP-qPCR. This study will provide insights on how RNAi and non-coding RNA transcripts function in centromere organization and implicate how centromeres are defined.