Abstract: From the very first time they set foot in the nuclear landscape till the end of their life, RNAs are packaged in ribonucleoproteins (RNPs) and face numerous processing steps to achieve function. To avoid the catastrophic consequences of naturally occurring processing errors, cells employ numerous quality control strategies. Focusing on yeast as a model system, we will review here how nuclear mechanisms ensure the proper assembly and maturation of mRNPs for their release in the cytoplasm, and highlight how these mechanisms are exploited to shape the RNA polymerase II transcriptome.