The U1 small nuclear ribonucleoprotein (snRNP) has an essential role in initiating spliceosome assembly, yet the mechanism underlying its synergy with other splicing regulators for efficient spliceosome assembly remains elusive. Here we identify zinc finger protein 207 (ZFP207) as a key regulator of U1 snRNP function that substantially promotes spliceosome assembly. Acute depletion of ZFP207 results in a series of molecular phenotypes indicative of U1 snRNP dysregulation. Mechanistically, the N-terminal zinc finger domains of ZFP207 directly bind to stem-loop 3 of U1 snRNA, while its C-terminal intrinsically disordered regions undergo phase separation to form biomolecular condensates with U1 snRNP. These condensates create a crowded molecular environment that increases the local concentration of splicing snRNPs and regulators, thereby accelerating the speed of spliceosome assembly by facilitating interactions between U1 snRNP and other snRNPs. Collectively, our study demonstrates the critical role of phase separation in ensuring effective U1 snRNP function and promoting efficient spliceosome assembly.
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http://dx.doi.org/10.1038/s41594-025-01501-z | DOI Listing |
In eukaryotes, the process of intron removal from nuclear pre-mRNA is performed by the spliceosome, a dynamic molecular machine composed of small nuclear ribonucleoproteins (snRNPs; U1, U2, U4, U5, and U6) and dozens of other protein splicing factors. The U6 snRNP contains the U6 snRNA and the proteins Prp24 and Lsm2-8 heteroheptamer. A key feature of the snRNP is a modified U6 snRNA 3' end, which in (yeast) contains a 3' phosphate.
View Article and Find Full Text PDFNat Struct Mol Biol
March 2025
Department of Cardiology of the Second Affiliated Hospital and Department of Cell Biology, Zhejiang University School of Medicine, Hangzhou, China.
The U1 small nuclear ribonucleoprotein (snRNP) has an essential role in initiating spliceosome assembly, yet the mechanism underlying its synergy with other splicing regulators for efficient spliceosome assembly remains elusive. Here we identify zinc finger protein 207 (ZFP207) as a key regulator of U1 snRNP function that substantially promotes spliceosome assembly. Acute depletion of ZFP207 results in a series of molecular phenotypes indicative of U1 snRNP dysregulation.
View Article and Find Full Text PDFCell Res
February 2025
Minhang Hospital & Institutes of Biomedical Sciences, Shanghai Key Laboratory of Medical Epigenetics, International Co-laboratory of Medical Epigenetics and Metabolism, Fudan University, Shanghai, China.
The spliceosome, a highly dynamic macromolecular assembly, catalyzes the precise removal of introns from pre-mRNAs. Recent studies have provided comprehensive structural insights into the step-wise assembly, catalytic splicing and final disassembly of the spliceosome. However, the molecular details of how the spliceosome recognizes and rejects suboptimal splicing substrates remained unclear.
View Article and Find Full Text PDFEur J Hum Genet
February 2025
Molecular Genetics and Functional Genomics, Bambino Gesù Children's Hospital, IRCCS, 00146, Rome, Italy.
A narrow spectrum of heterozygous variants in RNU4-2, encoding the small nuclear RNA (snRNA) U4, underlies ReNU syndrome, a neurodevelopmental disorder (NDD) characterized by moderate to severe developmental delay (DD), intellectual disability (ID), a distinctive facial gestalt, and multisystem involvement. Pathogenic variants have primarily been reported within an 18-nt critical region contributing to stabilizing the U4/U6 snRNA duplex and proper spliceosome assembly. By combining whole genome sequencing reanalysis and targeted direct sequencing in 190 molecularly unexplained NDD cases, we report on five affected individuals carrying pathogenic/putative pathogenic RNU4-2 variants (2.
View Article and Find Full Text PDFNucleic Acids Res
February 2025
Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, United States.
Spliceosome assembly and catalytic activation involve dozens of protein and snRNA binding and unbinding events. The B-complex specific proteins (Prp38, Snu23, and Spp381) have critical roles in stabilizing the spliceosome during rearrangements essential for activation. While these proteins are conserved, different mechanisms have been proposed for their recruitment to spliceosomes.
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