The ribonuclease DISL-2 mediates piRNA degradation in C. elegans

The PIWI/piRNA pathway serves as a conserved RNA-directed immune mechanism that suppresses transposons and promotes fertility. The biogenesis of piRNAs has been extensively investigated since their discovery, yet the mechanisms governing piRNA degradation remain poorly understood. This study determines the half-lives of thousands of C. elegans piRNAs, revealing a broad range from less than 1 hour to over 20 hours. Notably, piRNAs with 3' terminal uridines are degraded faster than those with 3' guanines or cytosines, suggesting that 3' uridines induce nucleolytic degradation. We identify DISL-2, a 3' to 5' exoribonuclease, as a key enzyme responsible for degrading piRNAs with templated 3' uridines as well as non-templated 3' uridines added by Poly(U) polymerase PUP-1. Furthermore, DISL-2 acts as a quality control factor to target piRNAs that are improperly processed at their 3' ends. Together, our findings advance the understanding of piRNA homeostasis by determining piRNA half-lives and identifying factors involved piRNA decay. Overall design: Analysis of piRNA half-lives measured by depletion of piRNA transcription factor TOFU-5. Analysis of piRNAs in disl-2 and pup-1 genetically null mutants compared to that in wild-type. mRNA sequencing of disl-2 mutants compared to that in wild-type. RNAs were isolated from gravid adult animals, subjected to high-throughput RNA sequencing anda analyzed.