Greg Hannon's group at Cold Spring Harbor Laboratory was one of many labs scrambling to identify Slicer, the enzyme doing the cutting in RNA-mediated interference. 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 Argonaute without actually saying it."












