Emerging themes in non-coding RNA quality control.

Quality control pathways for non-coding RNAs such as tRNAs and rRNAs are widespread. In both prokaryotes and eukaryotes, poly(A) polymerases target aberrant non-coding RNAs for degradation. In yeast, a nuclear complex that includes the poly(A) polymerase Trf4p works together with the exosome in degrading a broad array of non-coding RNAs, several of which are aberrant. Yeast also have additional pathways for the degradation of defective RNAs and other pathways may exist in higher eukaryotes. One possibility is that cells recognize specific, still undiscovered, features common to misfolded RNAs; however, an alternative is that RNA quality control proteins interact with relatively general RNA structures, whereas correctly folded RNAs are sequestered by specific RNA-binding proteins and thus protected from degradation. Recently available structures of protein and ribonucleoprotein complexes involved in non-coding RNA quality control are providing a more detailed understanding of this process.