Take the “A” tail – quality control of ribosomal and transfer RNA

The overall fidelity of RNA biosynthesis and processing is very high. This goes for both mRNAs, which are turned over relatively quickly, and for stable RNAs, such as the components of the translational apparatus, the transfer and ribosomal RNAs. However, no enzymatic process is completely error-free, so to minimize the number of non-functional transcripts, the cell has degradation pathways in place to efficiently deal with those mistakes that inevitably occur. Though several “RNA surveillance” or “RNA quality control” systems have been described that are able to specifically eliminate misfolded and non-functional RNAs, we still do not understand neither what precise features define a faulty RNA, nor the molecular basis for recognition of such molecules. Nonetheless, our knowledge about the controlled degradation of both stable and labile RNAs is now converging into a unified picture that points to the poly(A) tail as a key discriminator of RNA quality in both bacteria and eukaryotes.