Elastic Coupling Between RNA Degradation and Unwinding by an Exoribonuclease

Abstract

Loading a Spring To regulate cellular RNA levels, transcription must be balanced by RNA degradation. An important player is the exosome, which can unwind and degrade structured RNA. Lee et al. (p. 1726 ) used single-molecule fluorescence analysis to investigate how degradation and unwinding are coupled in the catalytic subunit of the yeast exosome complex, Rrp44. Rrp44 apparently digests several base pairs without unwinding, accumulates the energy, which it then uses to unwind four to five base pairs in a burst. Similar spring-like behavior has been proposed for conventional helicases, except that the stored energy comes from hydrolysis of adenosine triphosphate rather than the RNA polymer.