Cotranscriptional RNA checkpoints.

Transcription of protein-coding genes by RNA polymerase II is a repetitive, cyclic process that enables synthesis of multiple RNA molecules from the same template. The transcription cycle consists of three main stages, initiation, elongation and termination. Each of these phases is intimately coupled to a specific step in pre-mRNA processing; 5´ capping, splicing and 3´-end formation, respectively. In this article, we discuss the recent concept that cotranscriptional checkpoints operate during mRNA biogenesis to ensure that nonfunctional mRNAs with potentially deleterious effects for the cell are not produced or exported to the cytoplasm for translation.