The long term objective of this proposal is to elucidate the molecular mechanism of rDNA silencing, which is the SIR2- dependent suppression of recombination and RNA polymerase II (Pol II)-mediated transcription in the yeast ribosomal DNA (rDNA) locus. SIR2 is the founding member of an evolutionarily conserved gene family that has been implicated in transcriptional silencing, DNA repair, and meiosis checkpoint regulation in yeast. RDNA silencing was only recently identified and therefore provides a novel point of view to the investigation of chromatin effects on gene repression. Silencing of various tumor suppressor genes is well established as a step leading to cancer formation. Furthermore, regulation of ribosomal RNA transcription has also been implicated in cellular growth control. Therefore, understanding the basic mechanism of gene silencing in the rDNA will provide important insights to human disease processes and also the function of SIR2. Molecular genetic and biochemical approaches will be used to define the epigenetic factors controlling rDNA silencing and to classify it relative to the other known forms of silencing in yeast, telomere position effect (TPE) and repression of the silent mating type loci (HML and HMR). These approaches will also be used to determine the role of RNA polymerase I-mediated rRNA transcription in the silencing of Pol II-transcribed genes position within the rDNA. Finally, the role of NAD metabolism in regulating rDNA silencing will be molecularly dissected. The proposed work will also provide a framework for the future functional analysis of multiple rDNA silencing factors that have been identified.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM061692-05
Application #
6757238
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Carter, Anthony D
Project Start
2000-07-01
Project End
2005-06-30
Budget Start
2004-07-01
Budget End
2005-06-30
Support Year
5
Fiscal Year
2004
Total Cost
$214,600
Indirect Cost
Name
University of Virginia
Department
Biochemistry
Type
Schools of Medicine
DUNS #
065391526
City
Charlottesville
State
VA
Country
United States
Zip Code
22904
Hontz, Robert D; Niederer, Rachel O; Johnson, Joseph M et al. (2009) Genetic identification of factors that modulate ribosomal DNA transcription in Saccharomyces cerevisiae. Genetics 182:105-19
Hontz, Robert D; French, Sarah L; Oakes, Melanie L et al. (2008) Transcription of multiple yeast ribosomal DNA genes requires targeting of UAF to the promoter by Uaf30. Mol Cell Biol 28:6709-19
Dasgupta, Arindam; Ramsey, Kerrington L; Smith, Jeffrey S et al. (2004) Sir Antagonist 1 (San1) is a ubiquitin ligase. J Biol Chem 279:26830-8
Buck, Stephen W; Gallo, Christopher M; Smith, Jeffrey S (2004) Diversity in the Sir2 family of protein deacetylases. J Leukoc Biol 75:939-50
Gallo, Christopher M; Smith Jr, Daniel L; Smith, Jeffrey S (2004) Nicotinamide clearance by Pnc1 directly regulates Sir2-mediated silencing and longevity. Mol Cell Biol 24:1301-12
Buck, Stephen W; Sandmeier, Joseph J; Smith, Jeffrey S (2002) RNA polymerase I propagates unidirectional spreading of rDNA silent chromatin. Cell 111:1003-14
Sandmeier, Joseph J; French, Sarah; Osheim, Yvonne et al. (2002) RPD3 is required for the inactivation of yeast ribosomal DNA genes in stationary phase. EMBO J 21:4959-68
Sandmeier, Joseph J; Celic, Ivana; Boeke, Jef D et al. (2002) Telomeric and rDNA silencing in Saccharomyces cerevisiae are dependent on a nuclear NAD(+) salvage pathway. Genetics 160:877-89
Loewith, R; Smith, J S; Meijer, M et al. (2001) Pho23 is associated with the Rpd3 histone deacetylase and is required for its normal function in regulation of gene expression and silencing in Saccharomyces cerevisiae. J Biol Chem 276:24068-74