This is a family of eukaryotic proteins. Eukaryotic cells express a wide variety of endogenous small regulatory RNAs that regulate heterochromatin formation, developmental timing, defense against parasitic nucleic acids, and genome rearrangement. Many small regulatory RNAs are thought to function in nuclei, and in plants and fungi small interfering (si)RNAs associate with nascent transcripts and direct chromatin and/or DNA modifications. This family protein, NRDE-2, is required for small interfering (si)RNA-mediated silencing in nuclei. NRDE-2 associates with the Argonaute protein NRDE-3 within nuclei and is recruited by NRDE-3/siRNA complexes to nascent transcripts that have been targeted by RNA interference, RNAi, the process whereby double-stranded RNA (dsRNA) directs the sequence-specific degradation of mRNA.