Gene silencing by RNA interference (RNAi) has become a powerful tool for functional genomics. In the January 25 Science, Tijsterman et al. report a gene-silencing method induced by short (25 nucleotide) antisense RNA molecules (Science 2002, 295:694-697).

They found that injecting single-stranded, antisense RNA (asRNA) oligomers into the gonadal syncytium of Caenorhabditis elegans resulted in silencing of the maternal pos-1 gene and of germline-expressed genes. Tijsterman et al. found that asRNA silencing requires the mutator/RNAi genes mut-7 and mut-14. They cloned the mut-14 gene and reported that it encodes a putative RNA helicase with a DEAD-box motif.

The authors proposed that asRNA-induced gene-silencing may result from the priming of RNA synthesis on mRNA templates, thereby creating dsRNA for subsequent degradation.