The Hunting of the snRNP

The protein–RNA complexes known as snRNPs are the cell's editors. In 1992, researchers knew from many in vitro studies that different snRNPs band together to form the “spliceosome,” which splices premessenger RNA molecules to form functional mRNAs. But they didn't know where in the nucleus snRNPs congregated. Using a new technique, Angus Lamond (now at the University of Dundee, UK) and colleagues tracked snRNPs to two mysterious structures, the interchromatin granules and the Cajal bodies (formerly coiled bodies). Follow-up work suggests that both objects are important for snRNP production and activity.

When cell biologists first detected snRNPs using immunofluorescence, they observed glowing “speckles” strewn around the nucleus. Although this technique could reveal the presence of snRNPs, the antibodies initially available couldn't determine which kinds of snRNP mustered in a particular location....