In an advance, online publication of Nature this week, researchers at the University of Wisconsin-Madison report that "small regulatory RNAs inhibit RNA polymerase II during the elongation phase of transcription." They show that "gene nuclear RNAi defective-2 (nrde-2) encodes an evolutionarily conserved protein that is required for siRNA-mediated silencing in nuclei." The team suggests that their results "demonstrate that metazoan siRNAs can silence nuclear-localized RNAs co-trans