Figure 1. Possible mechanism for homology dependent gene silencing. The system can be fed by dsRNA or by other molecules originating from transposons or transgenes. These molecules are converted to 23-25 nt-long RNA molecules: guide RNA. The RDE-1 protein has been implicated in the step from dsRNA to guide RNA. These guide RNA molecules are within a proteinaceous complex, containing MUT-7, 8, 9 and RDE-2 and 3 proteins. This complex is then targeted to homologous RNA molecules. When a target RNA has been bound, it is degraded, possibly by two endonucleolytic breaks.