C. elegans hnRNPC Protects Genes from Transposon-mediated Disruption

All genomes harbor mobile genetic elements known as transposons and all organisms have evolved systems to prevent replication of these genomic parasites. Whether organisms also possess systems that allow them to tolerate and coexist with their transposons, post-mobilization, is not well understood. Here we describe the results of a forward genetic screen to identify factors that regulate DNA transposons in the C. elegans soma. The screen identified two nuclear-localized proteins: HRPC-1, the ortholog of mammalian heterogeneous nuclear ribonucleoprotein C (HNRNPC); and a nematode-specific protein we term STM-1. We find that HRPC-1 binds to introns containing DNA transposons and that this binding requires STM-1. HRPC-1 and STM-1 impede splicing, polyadenylation, and exonization of transposon-encoded RNAs. The results lead us to propose that one biological function of the C. elegans HNRNPC/STM-1 pathway is to prevent processing of DNA transposon-encoded RNAs, thereby limiting transposon activity and protecting host genes from transposon-mediated perturbations.