6gyt

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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To support their growth in a competitive environment and cause pathogenesis, bacteria have evolved a broad repertoire of macromolecular machineries to deliver specific effectors and toxins. Among these multiprotein complexes, the type VI secretion system (T6SS) is a contractile nanomachine that targets both prokaryotic and eukaryotic cells. The T6SS comprises two functional subcomplexes: a bacteriophage-related tail structure anchored to the cell envelope by a membrane complex. As in other contractile injection systems, the tail is composed of an inner tube wrapped by a sheath and built on the baseplate. In the T6SS, the baseplate is not only the tail assembly platform, but also docks the tail to the membrane complex and hence serves as an evolutionary adaptor. Here we define the biogenesis pathway and report the cryo-electron microscopy (cryo-EM) structure of the wedge protein complex of the T6SS from enteroaggregative Escherichia coli (EAEC). Using an integrative approach, we unveil the molecular architecture of the whole T6SS baseplate and its interaction with the tail sheath, offering detailed insights into its biogenesis and function. We discuss architectural and mechanistic similarities but also reveal key differences with the T4 phage and Mu phage baseplates.
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The transcriptional co-activator p300 is a histone acetyltransferase (HAT) that is typically recruited to transcriptional enhancers and regulates gene expression by acetylating chromatin. Here we show that the activation of p300 directly depends on the activation and oligomerization status of transcription factor ligands. Using two model transcription factors, IRF3 and STAT1, we demonstrate that transcription factor dimerization enables the trans-autoacetylation of p300 in a highly conserved and intrinsically disordered autoinhibitory lysine-rich loop, resulting in p300 activation. We describe a crystal structure of p300 in which the autoinhibitory loop invades the active site of a neighbouring HAT domain, revealing a snapshot of a trans-autoacetylation reaction intermediate. Substrate access to the active site involves the rearrangement of an autoinhibitory RING domain. Our data explain how cellular signalling and the activation and dimerization of transcription factors control the activation of p300, and therefore explain why gene transcription is associated with chromatin acetylation.
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Biogenesis and structure of a type VI secretion baseplate.,Cherrak Y, Rapisarda C, Pellarin R, Bouvier G, Bardiaux B, Allain F, Malosse C, Rey M, Chamot-Rooke J, Cascales E, Fronzes R, Durand E Nat Microbiol. 2018 Oct 15. pii: 10.1038/s41564-018-0260-1. doi:, 10.1038/s41564-018-0260-1. PMID:30323254<ref>PMID:30323254</ref>
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Transcription factor dimerization activates the p300 acetyltransferase.,Ortega E, Rengachari S, Ibrahim Z, Hoghoughi N, Gaucher J, Holehouse AS, Khochbin S, Panne D Nature. 2018 Oct;562(7728):538-544. doi: 10.1038/s41586-018-0621-1. Epub 2018 Oct, 15. PMID:30323286<ref>PMID:30323286</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 09:03, 14 November 2018

Transcription factor dimerization activates the p300 acetyltransferase

6gyt, resolution 2.50Å

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