Cancer-associated SNRPD3 Mutation Confers Resistance to Hypoxia, Which is Attenuated by DRP1 Inhibition

RNA splicing is a fundamental cellular mechanism performed by spliceosomes that synthesise multiple mature RNA isoforms from a single gene. The association between spliceosome abnormality and solid cancers remains largely unknown. Here, we demonstrated that Sm proteins, which are common components of the spliceosomes and constitute the Sm ring, were overexpressed in multiple cancers and their expression levels were correlated with clinical prognosis. In a pan-cancer mutational hotspot in the Sm ring at SNRPD3 G96V, we found that the G96V substitution confers resistance to hypoxia. RNA-seq detected numerous differentially spliced events between the wild-type and mutation-carrying cells cultured under hypoxia, wherein skipping exons and mutually exclusive exons were frequently observed. This was observed in DNM1L mRNA, which encodes the DRP1 protein that regulates mitochondrial fission. The mitochondria of cells carrying this mutation were excessively fragmented compared with those of wild-type cells. Furthermore, treatment with a DRP1 inhibitor (Mdivi-1) recovered the over-fragmented mitochondria, leading to the attenuation of hypoxia resistance in the mutant cells. These results propose a novel correlation between the cancer-related spliceosome abnormality and mitochondrial fission. Thus, targeting SNRPD3 G96V with a DRP1 inhibitor is a potential treatment strategy for cancers with spliceosome abnormalities.