From transcription to export: mRNA's winding path to the cytoplasm

In eukaryotes, the separation of transcription from translation enables extensive mRNA processing (capping, splicing, and polyadenylation) before translation. This review focuses on recent work that provides considerable insight into how mRNAs navigate these processes in which a spectrum of RNA-binding proteins (RBPs) coordinate different processing steps and couple them to nuclear export. Although the principal components in these pathways have been identified, the precise way in which RBPs bind to mRNAs, some aspects of how their binding and release are mediated by DEAD-box ATPases, and the complete structures of some messenger ribonucleoprotein complexes (mRNPs) remain unclear. Moreover, the checkpoints that recognize both completion of mRNA processing and the generation of mature mRNPs, as well as how they are coordinated, are only partially characterized.