First discovered only a few brief years ago, microRNAs are small, remarkably powerful molecules that appear to play a pivotal role in gene silencing, one of the body’s main strategies for regulating its genome. A scant 22 nucleotides in length, miRNAs appear to work by binding to and somehow interfering with messenger RNA, itself responsible for translating genes into proteins. But how do miRNAs arise? And what can we learn about their biological function from their origins? In a study published last year in Nature, researchers at The Wistar Institute identified a two-protein complex, called the microprocessor complex, which controls the earliest steps in the creation of miRNAs in the cell nucleus. Now, in a new study published online by Nature today, the Wistar group has identified a three-protein complex that picks up the process in the cell cytoplasm and carries it through to the maturation of the finished miRNAs.
