7OS1

Cryo-EM structure of Brr2 in complex with Fbp21

Summary for 7OS1

• Entry DOI: 10.2210/pdb7os1/pdb
• EMDB information: 13045
• Descriptor: U5 small nuclear ribonucleoprotein 200 kDa helicase, WW domain-binding protein 4 (2 entities in total)
• Functional Keywords: mrna splicing, spliceosomal assembly, splicing regulation, brr2 helicase, splicing
• Biological source: Homo sapiens (Human); More
• Total number of polymer chains: 2
• Total formula weight: 218994.56

Authors

Bergfort, A.,Hilal, T.,Weber, G.,Wahl, M.C. (deposition date: 2021-06-07, release date: 2022-02-23, Last modification date: 2024-07-17)

Primary citation

Bergfort, A.,Hilal, T.,Kuropka, B.,Ilik, I.A.,Weber, G.,Aktas, T.,Freund, C.,Wahl, M.C.
The intrinsically disordered TSSC4 protein acts as a helicase inhibitor, placeholder and multi-interaction coordinator during snRNP assembly and recycling.
Nucleic Acids Res., 50:2938-2958, 2022

PubMed Abstract: Biogenesis of spliceosomal small nuclear ribonucleoproteins (snRNPs) and their recycling after splicing require numerous assembly/recycling factors whose modes of action are often poorly understood. The intrinsically disordered TSSC4 protein has been identified as a nuclear-localized U5 snRNP and U4/U6-U5 tri-snRNP assembly/recycling factor, but how TSSC4's intrinsic disorder supports TSSC4 functions remains unknown. Using diverse interaction assays and cryogenic electron microscopy-based structural analysis, we show that TSSC4 employs four conserved, non-contiguous regions to bind the PRPF8 Jab1/MPN domain and the SNRNP200 helicase at functionally important sites. It thereby inhibits SNRNP200 helicase activity, spatially aligns the proteins, coordinates formation of a U5 sub-module and transiently blocks premature interaction of SNRNP200 with at least three other spliceosomal factors. Guided by the structure, we designed a TSSC4 variant that lacks stable binding to the PRPF8 Jab1/MPN domain or SNRNP200 in vitro. Comparative immunoprecipitation/mass spectrometry from HEK293 nuclear extract revealed distinct interaction profiles of wild type TSSC4 and the variant deficient in PRPF8/SNRNP200 binding with snRNP proteins, other spliceosomal proteins as well as snRNP assembly/recycling factors and chaperones. Our findings elucidate molecular strategies employed by an intrinsically disordered protein to promote snRNP assembly, and suggest multiple TSSC4-dependent stages during snRNP assembly/recycling.

PubMed: 35188580
DOI: 10.1093/nar/gkac087

Experimental method

ELECTRON MICROSCOPY (3.3 Å)