Guardians of splicing: quality control mechanisms of snRNA variants.

A new study by Ma and colleagues (doi:10.1101/gad.353690.126) identifies distinct quality control systems that degrade snRNA variants. Variants expressed from snRNA pseudogenes, deficient in 3' end processing or RNP assembly, are degraded by the nuclear RNA exosome or by cytoplasmic decay initiated by TUT4/7 enzymes. When variant snRNAs are stabilized, they can assemble into spliceosomes and alter splicing. Moreover, pathogenic mutations in canonical snRNA genes can trigger aberrant degradation by these quality control mechanisms, which may contribute to disease pathology. In summary, this work reveals how cells maintain a functional pool of snRNP complexes and links their dysregulation to human diseases.