Using biochemical mutagenesis, in vivo knockouts, and enzymatic assays, they had all but pegged Argonaute2. But, says Hannon, "We were stuck ? We could go right up to the edge of saying it was ...

siRNAs loaded in an Argonaute protein then target complementary single-stranded RNA (ssRNA) to guide specific gene silencing. Fukunaga and Doudna now show that SGS3 is an RNA-binding protein that ...