The difference was in the tail

25.03.13
A new RNA degrading enzyme in fission yeast points to a whole new ball game in the control of gene expression. Researchers from the Control of Gene Expression Lab together with collaborators from the IGC Telomere and Genome Stability Lab have identified an enzyme that seems to prefer RNA molecules with a tail of Us instead of the typical tail of As of messenger RNAs. The mere existence of polyU molecules suggests that a whole subset of RNA degrading processes has been hindered from researchers so far. The findings are published online in The EMBO Journal.

Cells control the expression of their genes at different levels. One strategy is to degrade the molecules that serve as intermediates between the information contained in DNA and the acting proteins, the messenger RNAs. The whole RNA degradation process is highly regulated: mRNA molecules are marked for destruction and ribonucleases (RNases) chop the mRNAs in pieces. In their work, researchers established that the newly identified RNase (code name: Dis3L2) acts independently from previously known pathways, in specific cellular locations.

What intrigued researchers the most was the nature of the messenger RNA found in their experiments. Typical mRNAs end with a tail of adenines (A) but in the absence of this new enzyme, the accumulated mRNAs displayed a tail of uridines (U). Cecília Arraiano, who coordinated this study, points out that “these mRNAs would have been invisible to traditional RNA techniques based on the existence of the polyA tail”.

Researchers believe that adding U nucleotides serves to tag mRNAs for fast removal by the identified enzyme, a process that also occurs in other organisms, including humans. Confident on the importance of this discovery Cecília Arraiano further speculates “this process is probably important in cells where polyU RNAs have been identified like stem cells and certain types of cancer.”

Original Article

The EMBO Journal AOP doi:10.1038/emboj.2013.63

The exoribonuclease Dis3L2 defines a novel eukaryotic RNA degradation pathway

The exonuclease Dis3L2 acts independently of the exosome in a novel pathway for cytoplasmic RNA turnover, preferentially degrading oligo-uridylated substrates.

Michal Malecki, Sandra C Viegas, Tiago Carneiro, Pawel Golik, Clémentine Dressaire, Miguel G Ferreira and Cecília M Arraiano