7bb3
From Proteopedia
Structure of S. pombe YG-box oligomer
Structural highlights
FunctionSMN_SCHPO The SMN complex catalyzes the assembly of small nuclear ribonucleoproteins (snRNPs), the building blocks of the spliceosome, and thereby plays an important role in the splicing of cellular pre-mRNAs (PubMed:20400941, PubMed:33754639, PubMed:10749974). Most spliceosomal snRNPs contain a common set of Sm proteins smb1, smd1, smd2, smd3, sme1, smf1 and smg1 that assemble in a heptameric protein ring on the Sm site of the small nuclear RNA to form the core snRNP (Sm core) (By similarity). In the cytosol, the Sm proteins smd1, smd2, sme1, smf1 and smg1 (5Sm) are trapped in an inactive 6S pICln-Sm complex by the chaperone saf5 that controls the assembly of the core snRNP (By similarity). To assemble core snRNPs, the SMN complex accepts the trapped 5Sm proteins from saf5 forming an intermediate (By similarity). Binding of snRNA inside 5Sm triggers eviction of the SMN complex, thereby allowing binding of smd3 and smb1 to complete assembly of the core snRNP (By similarity). Within the SMN complex, smn1 acts as a structural backbone and together with yip11/gem2 it gathers the Sm complex subunits (PubMed:33754639).[UniProtKB:Q16637][1] [2] [3] Publication Abstract from PubMedThe macromolecular SMN complex facilitates the formation of Sm-class ribonucleoproteins involved in mRNA processing (UsnRNPs). While biochemical studies have revealed key activities of the SMN complex, its structural investigation is lagging behind. Here we report on the identification and structural determination of the SMN complex from the lower eukaryote Schizosaccharomyces pombe, consisting of SMN, Gemin2, 6, 7, 8 and Sm proteins. The core of the SMN complex is formed by several copies of SMN tethered through its C-terminal alpha-helices arranged with alternating polarity. This creates a central platform onto which Gemin8 binds and recruits Gemins 6 and 7. The N-terminal parts of the SMN molecules extrude via flexible linkers from the core and enable binding of Gemin2 and Sm proteins. Our data identify the SMN complex as a multivalent hub where Sm proteins are collected in its periphery to allow their joining with UsnRNA. Identification and structural analysis of the Schizosaccharomyces pombe SMN complex.,Veepaschit J, Viswanathan A, Bordonne R, Grimm C, Fischer U Nucleic Acids Res. 2021 Jul 21;49(13):7207-7223. doi: 10.1093/nar/gkab158. PMID:33754639[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
| ||||||||||||||||||||
