piRNA 3' uridylation facilitates the assembly of MIWI/piRNA complex for efficient target regulation in mouse male germ cells.

Up to now, whether and how mature piRNAs undergo non-templated RNA 3' tailing modifications remains largely unclear in mammals. To learn more about the 3' tailing modification of piRNAs. We adopted a variety of different experimental methods and bioinformatics analysis in this study. Our findings suggest that tailing modifications on piRNAs should occur between pre-piRNA trimming by PNLDC1 and 2'-O-methylation by HENMT1. And interestingly, unlike MILI-bound and MIWI2-bound piRNAs, mono-uridylation was identified as the main tailing form on MIWI-bound piRNAs. Importantly, we found that 3' uridylation promotes piRNA binding to MIWI and in turn enhances the targeting capacity of MIWI/piRNA, supporting a functional importance of piRNA 3' uridylation in mouse male germ cells.