Abstract
A defining feature of centromeres is the presence of the histone H3 variant CENP-A(Cnp1). It is not known how CENP-A(Cnp1) is specifically delivered to, and assembled into, centromeric chromatin. Through a screen for factors involved in kinetochore integrity in fission yeast, we identified Sim3. Sim3 is homologous to known histone binding proteins NASP(Human) and N1/N2(Xenopus) and aligns with Hif1(S. cerevisiae), defining the SHNi-TPR family. Sim3 is distributed throughout the nucleoplasm, yet it associates with CENP-A(Cnp1) and also binds H3. Cells defective in Sim3 function have reduced levels of CENP-A(Cnp1) at centromeres (and increased H3) and display chromosome segregation defects. Sim3 is required to allow newly synthesized CENP-A(Cnp1) to accumulate at centromeres in S and G2 phase-arrested cells in a replication-independent mechanism. We propose that one function of Sim3 is to act as an escort that hands off CENP-A(Cnp1) to chromatin assembly factors, allowing its incorporation into centromeric chromatin.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Motifs
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Amino Acid Sequence
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Animals
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Autoantigens / genetics
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Autoantigens / metabolism*
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Binding Sites
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Blotting, Western
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Centromere / metabolism*
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Centromere Protein A
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Chromatin Immunoprecipitation
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Chromosomal Proteins, Non-Histone / genetics
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Chromosomal Proteins, Non-Histone / metabolism*
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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Green Fluorescent Proteins / genetics
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Green Fluorescent Proteins / metabolism
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Humans
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Microscopy, Fluorescence
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Molecular Sequence Data
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Mutation
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Protein Binding
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Protein Structure, Tertiary
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Protein Transport
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Schizosaccharomyces / chemistry
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Schizosaccharomyces / genetics
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Schizosaccharomyces / metabolism*
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Schizosaccharomyces pombe Proteins / genetics
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Schizosaccharomyces pombe Proteins / metabolism*
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Sequence Homology, Amino Acid
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Xenopus
Substances
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Autoantigens
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CENPA protein, human
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Centromere Protein A
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Chromosomal Proteins, Non-Histone
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Fungal Proteins
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NASP protein, human
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Nuclear Proteins
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Recombinant Fusion Proteins
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Schizosaccharomyces pombe Proteins
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Sim3 protein, S pombe
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Green Fluorescent Proteins