2io5
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(New page: 200px<br /><applet load="2io5" size="450" color="white" frame="true" align="right" spinBox="true" caption="2io5, resolution 2.700Å" /> '''Crystal structure o...)
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Revision as of 10:16, 21 November 2007
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Crystal structure of the CIA- histone H3-H4 complex
Overview
CIA (CCG1-interacting factor A)/ASF1, which is the most conserved histone, chaperone among the eukaryotes, was genetically identified as a factor for, an anti-silencing function (Asf1) by yeast genetic screening. Shortly, after that, the CIA-histone-H3-H4 complex was isolated from Drosophila as, a histone chaperone CAF-1 stimulator. Human CIA-I/II (ASF1a/b) was, identified as a histone chaperone that interacts with the bromodomain-an, acetylated-histone-recognizing domain-of CCG1, in the general, transcription initiation factor TFIID. Intensive studies have revealed, that CIA/ASF1 mediates nucleosome assembly by forming a complex with, another histone chaperone in human cells and yeast, and is involved in DNA, replication, transcription, DNA repair and silencing/anti-silencing in, yeast. CIA/ASF1 was shown as a major storage chaperone for soluble, histones in proliferating human cells. Despite all these biochemical and, biological functional analyses, the structure-function relationship of the, nucleosome assembly/disassembly activity of CIA/ASF1 has remained elusive., Here we report the crystal structure, at 2.7 A resolution, of CIA-I in, complex with histones H3 and H4. The structure shows the histone H3-H4, dimer's mutually exclusive interactions with another histone H3-H4 dimer, and CIA-I. The carboxy-terminal beta-strand of histone H4 changes its, partner from the beta-strand in histone H2A to that of CIA-I through large, conformational change. In vitro functional analysis demonstrated that, CIA-I has a histone H3-H4 tetramer-disrupting activity. Mutants with weak, histone H3-H4 dimer binding activity showed critical functional effects on, cellular processes related to transcription. The histone H3-H4, tetramer-disrupting activity of CIA/ASF1 and the crystal structure of the, CIA/ASF1-histone-H3-H4 dimer complex should give insights into mechanisms, of both nucleosome assembly/disassembly and nucleosome semi-conservative, replication.
About this Structure
2IO5 is a Protein complex structure of sequences from Homo sapiens and Xenopus laevis. Full crystallographic information is available from OCA.
Reference
Structure and function of the histone chaperone CIA/ASF1 complexed with histones H3 and H4., Natsume R, Eitoku M, Akai Y, Sano N, Horikoshi M, Senda T, Nature. 2007 Feb 11;. PMID:17293877
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