Project description:The S. cerevisiae Rpd3 large (Rpd3L) and small (Rpd3S) histone deacetylase (HDAC) complexes are prototypes for understanding transcriptional repression in eukaryotes [1]. The current view is that they function by deacetylating chromatin, thereby limiting accessibility of transcriptional factors to the underlying DNA. However, an Rpd3 catalytic mutant retains substantial repression capability when targeted to a promoter as a LexA fusion protein [2]. We investigated the HDAC-independent properties of the Rpd3 complexes biochemically and discovered a chaperone function, which promotes histone deposition onto DNA, and a novel activity, which prevents nucleosome eviction but not remodeling mediated by the ATP-dependent RSC complex. These HDAC-independent activities inhibit Pol II transcription on a nucleosomal template. The functions of the endogenous Rpd3 complexes can be recapitulated with recombinant Rpd3 core complex comprising Sin3, Rpd3, and Ume1. To test the hypothesis that Rpd3 contributes to chromatin stabilization in vivo, we measured histone H3 density genomewide and found that it was reduced at promoters in an Rpd3 deletion mutant but partially restored in a catalytic mutant. Importantly, the effects on H3 density are most apparent on RSC-enriched genes [3]. Our data suggest that the Rpd3 core complex could contribute to repression via a novel nucleosome stabilization function. H3 were ChIP'd from yeast strains and normalized to input.
Project description:The S. cerevisiae Rpd3 large (Rpd3L) and small (Rpd3S) histone deacetylase (HDAC) complexes are prototypes for understanding transcriptional repression in eukaryotes [1]. The current view is that they function by deacetylating chromatin, thereby limiting accessibility of transcriptional factors to the underlying DNA. However, an Rpd3 catalytic mutant retains substantial repression capability when targeted to a promoter as a LexA fusion protein [2]. We investigated the HDAC-independent properties of the Rpd3 complexes biochemically and discovered a chaperone function, which promotes histone deposition onto DNA, and a novel activity, which prevents nucleosome eviction but not remodeling mediated by the ATP-dependent RSC complex. These HDAC-independent activities inhibit Pol II transcription on a nucleosomal template. The functions of the endogenous Rpd3 complexes can be recapitulated with recombinant Rpd3 core complex comprising Sin3, Rpd3, and Ume1. To test the hypothesis that Rpd3 contributes to chromatin stabilization in vivo, we measured histone H3 density genomewide and found that it was reduced at promoters in an Rpd3 deletion mutant but partially restored in a catalytic mutant. Importantly, the effects on H3 density are most apparent on RSC-enriched genes [3]. Our data suggest that the Rpd3 core complex could contribute to repression via a novel nucleosome stabilization function.
Project description:Cells need to coordinate gene expression with their metabolic states to maintain cell homeostasis and growth. However, how cells transduce nutrient availability to appropriate gene expression response via histone modifications remains poorly understood. Here, we report that glycolysis promotes H3K4me3 by activating Tpk2, the catalytic subunit of protein kinase A (PKA) via the Ras-cyclic AMP (cAMP) pathway. Further study showed that Tpk2 antagonizes Jhd2-catalyzed H3K4 demethylation by phosphorylating Jhd2 at S321 and S340 in response to glucose availability.Mechanistically, Tpk2-catalyzed Jhd2 phosphorylation inhibits its overall binding to chromatin and promotes its polyubiquitination by the E3 ubiquitin ligase Not4 and degradation by the proteasome. In addition, Tpk2-catalyzed Jhd2 phosphorylation also maintains H3K14ac by preventing the binding of Rpd3 to chromatin. By inhibiting the activity of Jhd2 and Rpd3, Tpk2-catalyzed Jhd2 phosphorylation regulates gene expression and promotes autophagy. Thus, regulation of Jhd2 by the Ras-cAMP-PKA pathway shed lights on how cells rewire their biological responses to glucose availability.
Project description:Post-translational modification of proteins by lysine acetylation plays important regulatory roles in living cells. The budding yeast Saccharomyces cerevisiae is a widely used unicellular eukaryotic model organism in biomedical research. S. cerevisiae contains several evolutionary conserved lysine acetyltransferases and deacetylases. However, only a few dozen acetylation sites in S. cerevisiae are known, presenting a major obstacle for further understanding the regulatory roles of acetylation in this organism. Here we use high resolution mass spectrometry to identify about 4000 lysine acetylation sites in S. cerevisiae. Acetylated proteins are implicated in the regulation of diverse cytoplasmic and nuclear processes including chromatin organization, mitochondrial metabolism, and protein synthesis. Bioinformatic analysis of yeast acetylation sites shows that acetylated lysines are significantly more conserved compared with nonacetylated lysines. A large fraction of the conserved acetylation sites are present on proteins involved in cellular metabolism, protein synthesis, and protein folding. Furthermore, quantification of the Rpd3-regulated acetylation sites identified several previously known, as well as new putative substrates of this deacetylase. Rpd3 deficiency increased acetylation of the SAGA (Spt-Ada-Gcn5-Acetyltransferase) complex subunit Sgf73 on K33. This acetylation site is located within a critical regulatory domain in Sgf73 that interacts with Ubp8 and is involved in the activation of the Ubp8-containing histone H2B deubiquitylase complex. Our data provides the first global survey of acetylation in budding yeast, and suggests a wide-ranging regulatory scope of this modification. The provided dataset may serve as an important resource for the functional analysis of lysine acetylation in eukaryotes
Project description:These three replicates were analyzed in "Genomewide identification of Sko1 target promoters reveals a regulatory network that operates in response to osmotic stress in Saccharomyces cerevisiae. ", by Proft M, Gibbons FD, Copeland M, Roth FP, Struhl K; published in Eukaryot Cell. 2005 Aug;4(8):1343-52. A new analysis algorithm for Chip-chip data ('Chipper') is described in Genome Biology. Manuscript entitled "Chipper: discovering transcription-factor targets from chromatin immunoprecipitation microarrays using variance stabilization." by FD Gibbons, M Proft, K Struhl, and FP Roth. Accepted, no publication date as yet. Keywords: ChIP-chip