Abstract

In eukaryotes, double‐stranded RNAs (dsRNAs) or short, interfering dsRNAs (siRNAs) can reduce the accumulation of a sequence‐related mRNA, often resulting in a loss‐of‐function phenotype—a process termed RNA interference (RNAi). Unfortunately, some mRNAs are resistant to the effects of dsRNA. Experiments designed to unravel RNAi mechanisms in Caenorhabditis elegans have led to the identification of two worm proteins, RRF‐31,2 and, now, ERI‐1,3 that can inhibit RNAi responses. Animals defective in either protein can display enhanced RNAi phenotypes for mRNAs that were previously resistant to dsRNA. Since ERI‐1 is a conserved protein, development of procedures to enhance RNAi effectiveness in other systems may be possible. BioEssays 26:715–718, 2004. © 2004 Wiley Periodicals, Inc.