U6 snRNP-binding protein that functions as a recycling factor of the splicing machinery (PubMed:25753661). Promotes the initial reassembly of U4 and U6 snRNPs following their ejection from the spliceosome during its maturation (PubMed:25753661). Forms a complex composed of sart-3, terminal uridylyltransferase usip-1 and U6 snRNA; complex formation is mediated by usip-1 and sart-3 binding to U6 snRNA (PubMed:25753661). Associates with U4 and U6 snRNP complexes, probably by interacting with U4 and U6 snRNAs (PubMed:25753661). Ubiquitously expressed. Expressed in embryos, larvae and adults. Lethal at the young adult stage due to a ruptured vulva (PubMed:25753661). RNAi-mediated knockdown causes a partial reduction in the number of hatched embryos (PubMed:25753661). RNAi-mediated knockdown in a usip-1 (tm1897) mutant background causes complete embryonic lethality (PubMed:25753661).