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1: Cell. 2007 Jun 15;129(6):1153-64.
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Nonhistone Scm3 and histones CenH3-H4 assemble the core of centromere-specific nucleosomes.

Mizuguchi G, Xiao H, Wisniewski J, Smith MM, Wu C.

Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Building 37, Room 6068, Bethesda, MD 20892-4255, USA.

The budding yeast histone H3 variant, Cse4, replaces conventional histone H3 in centromeric chromatin and, together with centromere-specific DNA-binding factors, directs assembly of the kinetochore, a multiprotein complex mediating chromosome segregation. We have identified Scm3, a nonhistone protein that colocalizes with Cse4 and is required for its centromeric association. Bacterially expressed Scm3 binds directly to and reconstitutes a stoichiometric complex with Cse4 and histone H4 but not with conventional histone H3 and H4. A conserved acidic domain of Scm3 is responsible for directing the Cse4-specific interaction. Strikingly, binding of Scm3 can replace histones H2A-H2B from preassembled Cse4-containing histone octamers. This incompatibility between Scm3 and histones H2A-H2B is correlated with diminished in vivo occupancy of histone H2B, H2A, and H2AZ at centromeres. Our findings indicate that nonhistone Scm3 serves to assemble and maintain Cse4-H4 at centromeres and may replace histone H2A-H2B dimers in a centromere-specific nucleosome core.

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PMID: 17574026 [PubMed - indexed for MEDLINE]