Transcriptional silencing is a gene control mechanism resulting in epigenetic repression of large (>1 gene) chromosomal domains. This type of treanscriptional repression - which occurs near telomeres, in the nucleolar rDNA, and at the silent mating type loci of yeast - is correlated with significant changes in chromatin structure that are thought to limit the accessibility of the silenced chromosomal domains to transcriptional machinery. At least two types of proteins are intimately associated with silent chromatin in the yeast, Saccharomyces cerevisiae: Sir (silent information regulator) proteins and the core histones. The Sir2 protein is required for all forms of silencing, while Sir3 and Sir4 are required for telomeric and HM loci silencing only. Sir proteins are specifically associated with silent chromatin, although their precise roles in silencing remain to be elucidated. The N-terminal tails of histones H3 and H4, which are required for silencing at the silent mating type (HM) loci and at telomeres, are known to bind Sir3p and Sir4p. We and others have recently shown that Sir2p and its homologs are potent NAD-dependent protein deacetylases, whose substrates include the N-terminal tails of histones. While this observation has opened up a wealth of new possibilities regarding how genes are silenced, the underlying mechanisms are poorly understood. We will use the tools of molecular genetics, biochemistry and structural biology to carry out a comprehensive analysis of the molecular mechanisms involved in silencing.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM062385-03
Application #
6636558
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Carter, Anthony D
Project Start
2001-06-01
Project End
2005-05-31
Budget Start
2003-06-01
Budget End
2004-05-31
Support Year
3
Fiscal Year
2003
Total Cost
$310,650
Indirect Cost
Name
Johns Hopkins University
Department
Biochemistry
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21218
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Takahashi, Hidekazu; McCaffery, J Michael; Irizarry, Rafael A et al. (2006) Nucleocytosolic acetyl-coenzyme a synthetase is required for histone acetylation and global transcription. Mol Cell 23:207-17
Celic, Ivana; Masumoto, Hiroshi; Griffith, Wendell P et al. (2006) The sirtuins hst3 and Hst4p preserve genome integrity by controlling histone h3 lysine 56 deacetylation. Curr Biol 16:1280-9
Cosgrove, Michael S; Bever, Katherine; Avalos, Jose L et al. (2006) The structural basis of sirtuin substrate affinity. Biochemistry 45:7511-21
Avalos, Jose L; Bever, Katherine M; Wolberger, Cynthia (2005) Mechanism of sirtuin inhibition by nicotinamide: altering the NAD(+) cosubstrate specificity of a Sir2 enzyme. Mol Cell 17:855-68
Avalos, Jose L; Boeke, Jef D; Wolberger, Cynthia (2004) Structural basis for the mechanism and regulation of Sir2 enzymes. Mol Cell 13:639-48
Starai, V J; Takahashi, H; Boeke, J D et al. (2004) A link between transcription and intermediary metabolism: a role for Sir2 in the control of acetyl-coenzyme A synthetase. Curr Opin Microbiol 7:115-9
Starai, Vincent J; Takahashi, Hidekazu; Boeke, Jef D et al. (2003) Short-chain fatty acid activation by acyl-coenzyme A synthetases requires SIR2 protein function in Salmonella enterica and Saccharomyces cerevisiae. Genetics 163:545-55
Starai, V J; Celic, I; Cole, R N et al. (2002) Sir2-dependent activation of acetyl-CoA synthetase by deacetylation of active lysine. Science 298:2390-2
Avalos, Jose L; Celic, Ivana; Muhammad, Shabazz et al. (2002) Structure of a Sir2 enzyme bound to an acetylated p53 peptide. Mol Cell 10:523-35

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