Spliceosomal small nuclear ribonucleoprotein particles (snRNPs) undergo a complex maturation pathway containing multiple steps in the nucleus and in the cytoplasm. snRNP biogenesis is strictly proofread and several quality control checkpoints are placed along the pathway. Here, we analyzed the fate of small nuclear RNAs (snRNAs) that are unable to acquire a ring of Sm proteins. We showed that snRNAs lacking the Sm ring are unstable and accumulate in P-bodies in an LSm1-dependent manner. We further provide evidence that defective snRNAs without the Sm binding site are uridylated at the 3' end and associate with DIS3L2 3'→5' exoribonuclease and LSm proteins. Finally, inhibition of 5'→3' exoribonuclease XRN1 increases association of ΔSm snRNAs with DIS3L2, which indicates competition and compensation between these two degradation enzymes. Together, we provide evidence that defective snRNAs without the Sm ring are uridylated and degraded by alternative pathways involving either DIS3L2 or LSm proteins and XRN1.

• MeSH
• Exoribonucleases metabolism   MeSH
• HeLa Cells MeSH
• Nucleic Acid Conformation * MeSH
• Humans MeSH
• Organelles metabolism   MeSH
• SMN Complex Proteins metabolism   MeSH
• RNA-Binding Proteins metabolism   MeSH
• Proto-Oncogene Proteins metabolism   MeSH
• RNA, Small Nuclear chemistry   metabolism   MeSH
• Base Sequence MeSH
• RNA Stability MeSH
• RNA Transport * MeSH
• Protein Binding MeSH
• Binding Sites MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DIS3L2 protein, human MeSH Browser
• Exoribonucleases MeSH
• GEMIN5 protein, human MeSH Browser
• LSM1 protein, human MeSH Browser
• SMN Complex Proteins MeSH
• RNA-Binding Proteins MeSH
• Proto-Oncogene Proteins MeSH
• RNA, Small Nuclear MeSH

Spliceosomal snRNPs are complex particles that proceed through a fascinating maturation pathway. Several steps of this pathway are closely linked to nuclear non-membrane structures called Cajal bodies. In this review, I summarize the last 20 y of research in this field. I primarily focus on snRNP biogenesis, specifically on the steps that involve Cajal bodies. I also evaluate the contribution of the Cajal body in snRNP quality control and discuss the role of snRNPs in Cajal body formation.

• MeSH
• Coiled Bodies metabolism   MeSH
• Transcription, Genetic MeSH
• Humans MeSH
• RNA Processing, Post-Transcriptional MeSH
• Ribonucleoproteins, Small Nuclear genetics   metabolism   MeSH
• Spliceosomes MeSH
• Protein Binding MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Ribonucleoproteins, Small Nuclear MeSH