View source for 8qp8


==Cryo-EM Structure of Pre-B Complex (core part)==
<StructureSection load='8qp8' size='340' side='right'caption='[[8qp8]], [[Resolution|resolution]] 3.50&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8qp8]] is a 10 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8QP8 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8QP8 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Electron Microscopy, [[Resolution|Resolution]] 3.5&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=IHP:INOSITOL+HEXAKISPHOSPHATE'>IHP</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=8qp8 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8qp8 OCA], [https://pdbe.org/8qp8 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8qp8 RCSB], [https://www.ebi.ac.uk/pdbsum/8qp8 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8qp8 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/SF3A1_HUMAN SF3A1_HUMAN] Subunit of the splicing factor SF3A required for 'A' complex assembly formed by the stable binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. Sequence independent binding of SF3A/SF3B complex upstream of the branch site is essential, it may anchor U2 snRNP to the pre-mRNA. May also be involved in the assembly of the 'E' complex.
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Early spliceosome assembly can occur through an intron-defined pathway, whereby U1 and U2 small nuclear ribonucleoprotein particles (snRNPs) assemble across the intron(1). Alternatively, it can occur through an exon-defined pathway(2-5), whereby U2 binds the branch site located upstream of the defined exon and U1 snRNP interacts with the 5' splice site located directly downstream of it. The U4/U6.U5 tri-snRNP subsequently binds to produce a cross-intron (CI) or cross-exon (CE) pre-B complex, which is then converted to the spliceosomal B complex(6,7). Exon definition promotes the splicing of upstream introns(2,8,9) and plays a key part in alternative splicing regulation(10-16). However, the three-dimensional structure of exon-defined spliceosomal complexes and the molecular mechanism of the conversion from a CE-organized to a CI-organized spliceosome, a pre-requisite for splicing catalysis, remain poorly understood. Here cryo-electron microscopy analyses of human CE pre-B complex and B-like complexes reveal extensive structural similarities with their CI counterparts. The results indicate that the CE and CI spliceosome assembly pathways converge already at the pre-B stage. Add-back experiments using purified CE pre-B complexes, coupled with cryo-electron microscopy, elucidate the order of the extensive remodelling events that accompany the formation of B complexes and B-like complexes. The molecular triggers and roles of B-specific proteins in these rearrangements are also identified. We show that CE pre-B complexes can productively bind in trans to a U1 snRNP-bound 5' splice site. Together, our studies provide new mechanistic insights into the CE to CI switch during spliceosome assembly and its effect on pre-mRNA splice site pairing at this stage.

Structural insights into the cross-exon to cross-intron spliceosome switch.,Zhang Z, Kumar V, Dybkov O, Will CL, Zhong J, Ludwig SEJ, Urlaub H, Kastner B, Stark H, Luhrmann R Nature. 2024 May 22. doi: 10.1038/s41586-024-07458-1. PMID:38778104<ref>PMID:38778104</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 8qp8" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Dybkov O]]
[[Category: Kastner B]]
[[Category: Kumar V]]
[[Category: Ludwig S]]
[[Category: Luehrmann R]]
[[Category: Stark H]]
[[Category: Urlaub H]]
[[Category: Will CL]]
[[Category: Zhang Z]]
[[Category: Zhong J]]