| Double-stranded RNA-mediated gene interference (RNAi) in Caenorhabditis elegans systemically inhibits gene expression throughout the organism. Much has been learned about the general mechanism of RNAi, but little is known about the systemic aspect. To investigate how gene-specific silencing information is transmitted between cells, a strain that permits visualization of systemic RNAi was constructed. This strain was used in a genetic screen to identify systemic RNA interference defective (sid) mutants. The identified loci are required to spread gene-silencing information between tissues, but not to initiate or maintain an RNAi response. One of these loci, sid-1, encodes a conserved protein with predicted transmembrane domains. SID-1 is expressed in cells sensitive to RNAi, has enriched localization at the cell periphery, and its function is required cell-autonomously for systemic RNAi. Characterization of the RNAi resistance of sid-2 and sid-3 mutants, as well as the progress towards cloning these two genes is also described. |
