research: trampling on rna

30 September 2005

Eukaryotic cells produce a huge amount of RNA, but this is seldom used 'as is'. In most cases, long precursor RNAs are processed and trimmed into mature forms, ready to be used as templates for protein synthesis or as components of the protein factories themselves, the ribosomes.

The 'exosome' plays a key role in this processing, as well as in degrading defective RNAs that fail quality control checks. On its own, in a test tube, this complex of ten exonucleases that chew up RNA from one end works rather slowly – so researchers thought that its activity in cells might be boosted by additional factors.

David Tollervey and colleagues in Edinburgh, who originally identified the exosome, have now found the factors that accelerate exosome processing. The TRAMP complex (short for the Trf4p/Air2p/Mtr4p polyadenylation complex) adds a poly(A) tail to ribosomal RNA and small nucleolar RNA, which promotes their degradation in the nucleus by the exosome.

La Cava J et al. RNA degradation by the exosome is promoted by a nuclear polyadenylation complex. Cell 2005;121(5):713–24.