Enzyme measures RNA using natural ruler
For almost a decade, researchers have taken advantage of a powerful process called RNA interference (RNAi) to turn off certain genes in lab organisms and cell cultures (SN: 7/2/05, p. 7: Available to subscribers at Sound Off). Cells also use RNAi as a natural tool in immunity, development, and gene rearrangements within chromosomes. The process begins when a cell chews double-stranded RNA into bite-size fragments of about 25 base pairs, the chemical building blocks of RNA.
Scientists knew that an enzyme called dicer carries out this chopping task, but they hadn’t figured out how dicer measures lengths of RNA so precisely. A new study of dicer’s chemical structure suggests that the enzyme carries a built-in ruler.