View source for 8qo9


==Cryo-EM structure of a human spliceosomal B complex protomer==
<StructureSection load='8qo9' size='340' side='right'caption='[[8qo9]], [[Resolution|resolution]] 5.29&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8qo9]] is a 12 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=8QO9 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8QO9 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]] 5.29&#8491;</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=8qo9 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8qo9 OCA], [https://pdbe.org/8qo9 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8qo9 RCSB], [https://www.ebi.ac.uk/pdbsum/8qo9 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8qo9 ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/SF3B4_HUMAN SF3B4_HUMAN] Defects in SF3B4 are the cause of acrofacial dysostosis type 1 (AFD1) [MIM:[https://omim.org/entry/154400 154400]. AFD1 is a form of acrofacial dysostosis, a group of disorders which are characterized by malformation of the craniofacial skeleton and the limbs. The major facial features of AFD1 include downslanted palpebral fissures, midface retrusion, and micrognathia, the latter of which often requires the placement of a tracheostomy in early childhood. Limb defects typically involve the anterior (radial) elements of the upper limbs and manifest as small or absent thumbs, triphalangeal thumbs, radial hyoplasia or aplasia, and radioulnar synostosis. Phocomelia of the upper limbs and, occasionally, lower-limb defects have also been reported.<ref>PMID:22541558</ref> 
== Function ==
[https://www.uniprot.org/uniprot/SF3B4_HUMAN SF3B4_HUMAN] Subunit of the splicing factor SF3B 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. SF3B4 has been found in complex 'B' and 'C' as well. Belongs also to the minor U12-dependent spliceosome, which is involved in the splicing of rare class of nuclear pre-mRNA intron.
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The B complex is a key intermediate stage of spliceosome assembly. To improve the structural resolution of monomeric, human spliceosomal B (hB) complexes and thereby generate a more comprehensive hB molecular model, we determined the cryo-EM structure of B complex dimers formed in the presence of ATP gamma S. The enhanced resolution of these complexes allows a finer molecular dissection of how the 5' splice site (5'ss) is recognized in hB, and new insights into molecular interactions of FBP21, SNU23 and PRP38 with the U6/5'ss helix and with each other. It also reveals that SMU1 and RED are present as a heterotetrameric complex and are located at the interface of the B dimer protomers. We further show that MFAP1 and UBL5 form a 5' exon binding channel in hB, and elucidate the molecular contacts stabilizing the 5' exon at this stage. Our studies thus yield more accurate models of protein and RNA components of hB complexes. They further allow the localization of additional proteins and protein domains (such as SF3B6, BUD31 and TCERG1) whose position was not previously known, thereby uncovering new functions for B-specific and other hB proteins during pre-mRNA splicing.

Cryo-EM analyses of dimerized spliceosomes provide new insights into the functions of B complex proteins.,Zhang Z, Kumar V, Dybkov O, Will CL, Urlaub H, Stark H, Luhrmann R EMBO J. 2024 Mar;43(6):1065-1088. doi: 10.1038/s44318-024-00052-1. Epub 2024 Feb , 21. PMID:38383864<ref>PMID:38383864</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 8qo9" style="background-color:#fffaf0;"></div>

==See Also==
*[[U5-15kD|U5-15kD]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Dybkov O]]
[[Category: Kumar V]]
[[Category: Luehrmann R]]
[[Category: Stark H]]
[[Category: Urlaub H]]
[[Category: Will CL]]
[[Category: Zhang Z]]