3zco

Crystal structure of S. cerevisiae Sir3 C-terminal domain

spinqualitylabelsall models 3zco, resolution 2.70Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3zco is a 1 chain structure with sequence from Atcc 18824. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [SIR3_YEAST] The proteins SIR1 through SIR4 are required for transcriptional repression of the silent mating type loci, HML and HMR. The proteins SIR2 through SIR4 repress mulitple loci by modulating chromatin structure. Involves the compaction of chromatin fiber into a more condensed form. Publication Abstract from PubMed Gene silencing in budding yeast relies on the binding of the Silent Information Regulator (Sir) complex to chromatin, which is mediated by extensive interactions between the Sir proteins and nucleosomes. Sir3, a divergent member of the AAA+ ATPase-like family, contacts both the histone H4 tail and the nucleosome core. Here, we present the structure and function of the conserved C-terminal domain of Sir3, comprising 138 amino acids. This module adopts a variant winged helix-turn-helix (wH) architecture that exists as a stable homodimer in solution. Mutagenesis shows that the self-association mediated by this domain is essential for holo-Sir3 dimerization. Its loss impairs Sir3 loading onto nucleosomes in vitro and eliminates silencing at telomeres and HM loci in vivo. Replacing the Sir3 wH domain with an unrelated bacterial dimerization motif restores both HM and telomeric repression in sir3Delta cells. In contrast, related wH domains of archaeal and human members of the Orc1/Sir3 family are monomeric and have DNA binding activity. We speculate that a dimerization function for the wH evolved with Sir3's ability to facilitate heterochromatin formation. Dimerization of Sir3 via its C-terminal winged helix domain is essential for yeast heterochromatin formation.,Oppikofer M, Kueng S, Keusch JJ, Hassler M, Ladurner AG, Gut H, Gasser SM EMBO J. 2013 Feb 6;32(3):437-49. doi: 10.1038/emboj.2012.343. Epub 2013 Jan 8. PMID:23299941 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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