The Mechanism of RNA Interference and the Transposon Silencing inCaenorhabditis elegans

Abstract

All isolates of C. elegans contain multiple transposable elements in their genome. These elements jump around freely in somatic cells, but transposition is fully silenced in the germline. In investigating the mechanism of transposon silencing, we found that it was mechanistically linked to another phenomenon: RNAi or RNA interference. This is the experimental silencing of gene expression by administration of double-stranded RNA. METHOD. Mutants have been isolated that were defective in transposon silencing and/or in RNA interference. Several of these mutants have now been identified at the molecular level, thus defining essential components of the silencing machinery. The first biochemical analysis of the mechanism of silencing has also been initiated. RESULTS. Our current picture of the pathway of silencing is shown in Fig. 1. (Marcel) Several of the mutator proteins will be discussed in detail.

RNA Helicase MUT-14-Dependent Gene Silencing Triggered in C. elegans by Short Antisense RNAs

“…The loss of expression is confined to the injected gonad, indicating that, other than for long dsRNA, the asRNAs do not induce RNAi systemically. In contrast, we did not observe loss of GFP when GFP was expressed in a range of somatic tissues (9), which suggests that the time and range of target expression are crucial for the susceptibility of mRNA to as-RNA triggers. A distinction between germline versus somatic expression is, however, not absolute; (i) we could trigger RNAi with unc-22 asRNAs albeit with low frequency, and (ii) not all germline-expressed genes were susceptible (9).…”