mRNP quality control goes regulatory

The accuracy of eukaryotic gene expression relies on efficient quality control (QC). Most steps in the gene expression pathway en route from transcription to translation are error-prone and QC systems have evolved to utilise many of these biochemical processes as checkpoints to monitor the production or function of mRNA-protein particles (mRNPs). Mechanistically, such evaluation of mRNP fitness is based on competition between the opposing activities of mRNP biogenesis and/or function and mRNP turnover. In fact, quite subtle alteration of any parameter can tip the balance between mRNP persistence and degradation and, therefore, QC checkpoints also comprise perfect opportunities for controlling cellular levels of individual or even entire families of transcripts. From this perspective, QC and gene regulation represent two outcomes of the same molecular process.