View source for 8siy


==Origin Recognition Complex Associated (ORCA) protein bound to H4K20me3-nucleosome==
<StructureSection load='8siy' size='340' side='right'caption='[[8siy]], [[Resolution|resolution]] 2.90&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8siy]] is a 12 chain structure with sequence from [https://en.wikipedia.org/wiki/Rattus_norvegicus Rattus norvegicus], [https://en.wikipedia.org/wiki/Xenopus_laevis Xenopus laevis] and [https://en.wikipedia.org/wiki/Synthetic_construct Synthetic construct]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8SIY OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8SIY 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]] 2.9&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ML3:2-{[(2R)-2-AMINO-2-CARBOXYETHYL]SULFANYL}-N,N,N-TRIMETHYLETHANAMINIUM'>ML3</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=8siy FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8siy OCA], [https://pdbe.org/8siy PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8siy RCSB], [https://www.ebi.ac.uk/pdbsum/8siy PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8siy ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/A0A140UHX1_RAT A0A140UHX1_RAT] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Eukaryotic cells use chromatin marks to regulate the initiation of DNA replication. The origin recognition complex (ORC)-associated protein ORCA plays a critical role in heterochromatin replication in mammalian cells by recruiting the initiator ORC, but the underlying mechanisms remain unclear. Here, we report crystal and cryo-electron microscopy structures of ORCA in complex with ORC's Orc2 subunit and nucleosomes, establishing that ORCA orchestrates ternary complex assembly by simultaneously recognizing a highly conserved peptide sequence in Orc2, nucleosomal DNA, and repressive histone trimethylation marks through an aromatic cage. Unexpectedly, binding of ORCA to nucleosomes prevents chromatin array compaction in a manner that relies on H4K20 trimethylation, a histone modification critical for heterochromatin replication. We further show that ORCA is necessary and sufficient to specifically recruit ORC into chromatin condensates marked by H4K20 trimethylation, providing a paradigm for studying replication initiation in specific chromatin contexts. Collectively, our findings support a model in which ORCA not only serves as a platform for ORC recruitment to nucleosomes bearing specific histone marks but also helps establish a local chromatin environment conducive to subsequent MCM2-7 loading.

A dual role for the chromatin reader ORCA/LRWD1 in targeting the origin recognition complex to chromatin.,Sahu S, Ekundayo BE, Kumar A, Bleichert F EMBO J. 2023 Sep 18;42(18):e114654. doi: 10.15252/embj.2023114654. Epub 2023 Aug , 8. PMID:37551430<ref>PMID:37551430</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 8siy" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Rattus norvegicus]]
[[Category: Synthetic construct]]
[[Category: Xenopus laevis]]
[[Category: Bleichert F]]
[[Category: Ekundayo BE]]