Abstract
The N-terminal domain of the largest subunit of the Saccharomyces cerevisiae origin recognition complex (Orc1p) functions in transcriptional silencing and contains a bromo-adjacent homology (BAH) domain found in some chromatin-associated proteins including Sir3p. The 2.2 A crystal structure of the N-terminal domain of Orc1p revealed a BAH core and a non-conserved helical sub-domain. Mutational analyses demonstrated that the helical sub-domain was necessary and sufficient to bind Sir1p, and critical for targeting Sir1p primarily to the cis-acting E silencers at the HMR and HML silent chromatin domains. In the absence of the BAH domain, approximately 14-20% of cells in a population were silenced at the HML locus. Moreover, the distributions of the Sir2p, Sir3p and Sir4p proteins, while normal, were at levels lower than found in wild-type cells. Thus, in the absence of the Orc1p BAH domain, HML resembled silencing of genes adjacent to telomeres. These data are consistent with the view that the Orc1p-Sir1p interaction at the E silencers ensures stable inheritance of pre-established Sir2p, Sir3p and Sir4p complexes at the silent mating type loci.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Binding Sites
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Chromatin / metabolism
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Crystallography, X-Ray
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DNA-Binding Proteins / chemistry*
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DNA-Binding Proteins / physiology
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Gene Expression Regulation, Fungal*
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Gene Silencing*
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Histone Deacetylases / metabolism
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Macromolecular Substances
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Models, Molecular
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Molecular Sequence Data
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Origin Recognition Complex
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Protein Binding
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Protein Conformation
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Protein Structure, Tertiary
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Saccharomyces cerevisiae / genetics*
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Saccharomyces cerevisiae Proteins / chemistry*
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Saccharomyces cerevisiae Proteins / metabolism
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Saccharomyces cerevisiae Proteins / physiology
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Sequence Alignment
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Sequence Homology, Amino Acid
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Silent Information Regulator Proteins, Saccharomyces cerevisiae*
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Sirtuin 2
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Sirtuins
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Structure-Activity Relationship
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Trans-Activators / metabolism
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Transcription, Genetic
Substances
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Chromatin
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DNA-Binding Proteins
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Macromolecular Substances
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Origin Recognition Complex
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SIR1 protein, S cerevisiae
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SIR3 protein, S cerevisiae
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SIR4 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Silent Information Regulator Proteins, Saccharomyces cerevisiae
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Trans-Activators
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SIR2 protein, S cerevisiae
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Sirtuin 2
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Sirtuins
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Histone Deacetylases