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Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Cohesin releases DNA through asymmetric ATPase-driven ring opening

ABSTRACT: Cohesin stably holds together the sister chromatids from S phase until mitosis. To do so, cohesin must be protected against its cellular antagonist Wapl. Eco1 acetylates cohesinâs Smc3 subunit, which locks together the sister DNAs. We used yeast genetics to dissect how Wapl drives cohesin from chromatin and identified mutants of cohesin that are impaired in ATPase activity but remarkably confer robust cohesion that bypasses the need for the cohesin protectors Eco1 in yeast and Sororin in human cells. We uncover an unexpected functional asymmetry within the heart of cohesinâs highly conserved ABC-like ATPase machinery and show that an activity associated with one of cohesinâs two ATPase sites drives DNA release from cohesin rings. This key mechanism is conserved from yeast to humans. We propose that Eco1 locks cohesin rings around the sister chromatids by counteracting an asymmetric cohesin-associated ATPase activity. Effect of mutations in Smc1 and Smc3 on cohesin loading onto chromosomes

ORGANISM(S): Saccharomyces cerevisiae

SUBMITTER: Kim Nasmyth

PROVIDER: E-GEOD-76891 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Releasing activity disengages cohesinâs Smc3/Scc1 interface in a process blocked by acetylation

Project description:Sister chromatid cohesion conferred by entrapment of sister DNAs within a tripartite ring formed between cohesinâs Scc1, Smc1, and Smc3 subunits is generated during S and eventually destroyed at anaphase through cleavage of Scc1 by separase. Throughout the cell cycle, cohesinâs association with chromosomes is controlled by opposing activities: loading by the Scc2/4 complex and release by a separase independent releasing activity. Co-entrapment of sister DNAs during replication is accompanied by acetylation of Smc3 by Eco1, which blocks releasing activity and ensures that sisters remain stably connected. Because fusion of Smc3 to Scc1 prevents release and bypasses the requirement for Eco1, we suggested that release is mediated by disengagement of the Smc3/Scc1 interface. We now show that all mutations capable of bypassing Eco1, be they in cohesinâs Smc1, Smc3, Scc1,Wapl, Pds5, or Scc3 subunits, greatly reduce dissociation of N-terminal cleavage fragments of Scc1 (NScc1) from Smc3. We show that this process involves interaction between Smc ATPase heads and is inhibited by Smc3 acetylation Effect of mutations QQ and EQ in Smc3 on cohesin loading onto chromosomes

2016-02-18 | E-GEOD-76890 | biostudies-arrayexpress

Biological chromodynamics: a general method for measuring protein occupancy across the genome by calibrating ChIP-seq

Project description:Sequencing DNA fragments associated with proteins following in vivo cross-linking with formaldehyde (known as ChIP-seq) has been used extensively to describe the distribution of proteins across genomes. It is not widely appreciated that this method merely estimates a protein’s distribution and cannot reveal changes in occupancy between samples. To do this, we tagged with the same epitope orthologous proteins in Saccharomyces cerevisiae and Candida glabrata, whose sequences have diverged to a degree that most DNA fragments longer than 50 bp are unique to just one species. By mixing defined numbers of C.glabrata cells (the calibration genome) with S.cerevisiae samples (the experimental genomes) prior to chromatin fragmentation and immunoprecipitation, it is possible to derive a quantitative measure of occupancy (the occupancy ratio – OR) that enables a comparison of occupancies not only within but also between genomes. We demonstrate for the first time that this “internal standard” calibration method satisfies the sine qua non for quantifying ChIP-seq profiles, namely linearity over a wide range. Crucially, by employing functional tagged proteins, our calibration process describes a method that distinguishes genuine association within ChIP-seq profiles from background noise. Our method is applicable to any protein, not merely highly conserved ones, and obviates the need for the time consuming, expensive, and technically demanding quantification of ChIP using PCR, which can only be performed on individual loci. As we demonstrate for the first time in this paper, calibrated ChIP-seq represents a major step towards documenting the quantitative distributions of proteins along chromosomes in different cell states, which we term biological chromodynamics. Develop a method for quantitative ChIP-seq

2015-07-10 | E-GEOD-69907 | biostudies-arrayexpress

Inhibiting Fungal Multidrug Resistance by Disrupting an Activator-Mediator Interaction With the Small Molecule iKIX1

Project description:Eukaryotic transcription activators stimulate the expression of specific sets of target genes through recruitment of co-activators such as the RNA polymerase II-interacting Mediator complex. We previously identified an activator-targeted ~85 amino acid three-helix bundle KIX domain in the human MED15 Mediator subunit that is structurally conserved in Gal11 Mediator subunits in fungi. The Gal11 KIX domain is engaged by pleiotropic drug resistance transcription factor (Pdr1) orthologues, key regulators of the multidrug resistance (MDR) pathway in S. cerevisiae and in the clinically important human pathogen Candida glabrata. Drug-resistant clinical isolates of C. glabrata most commonly harbour point mutations in Pdr1 that render it constitutively active, suggesting that this transcriptional activation pathway may represent a lynchpin in C. glabrata MDR. We have now carried out sequential biochemical and in vivo high-throughput screens to identify small molecule inhibitors of the interaction of the C. glabrata Pdr1 activation domain with the C. glabrata Gal11A KIX domain. The lead compound (iKIX1) inhibits Pdr1-dependent gene activation in both S. cerevisiae and C. glabrata and re-sensitizes drug-resistant C. glabrata to effective azole antifungal concentrations in vitro and in animal models for disseminated and urinary tract C. glabrata infection. Samples are generated in triplicate for four conditions (DMSO/vehicle-treated, iKIX1-treated, DMSO/vehicle and ketoconazole-treated. and iKIX1-ketoconazole treated) in both Saccharomyces cerevisiae and Candida glabrata

2015-12-15 | E-GEOD-74361 | biostudies-arrayexpress

Microarray analysis comparing yeast Eco1 mutant W216G to mutants of FOB1 and RAD61

Project description:Eco1 is an acetyltransferase subunit of the cohesin complex and acts during DNA replication to establish cohesion between sister chromatids. However, cohesin has additional functions in gene expression, DNA damage repair, and higher-order organization of chromosomes. The eco1 mutant W216G disrupts acetyltansferase activity, and causes genome-wide transcriptional defects which can be suppressed by deletion of FOB1, a gene also involved in DNA replication. This experiment investigates gene expression differences between the eco1-W216G mutant, and mutants in FOB1, and RAD61 a gene involved in inhibition of cohesion establishment but mutation of which is able to suppress temperature sensitivity of the eco1-W216G mutant. Wt and mutant strains of yeast were grown to mid log phase in liquid culture in triplicate and harvested for comparison on Affymetrix microarrays. The following strains were compared: 1) eco1-W216G, 2) eco1-W216G fob1Δ, 3) eco1-W216G rad61Δ, 4) fob1Δ, 5) rad61Δ, and 6) WT.

2014-04-03 | E-GEOD-54741 | biostudies-arrayexpress

Cohesin releases DNA through asymmetric ATPase-driven ring opening

Project description:Cohesin stably holds together the sister chromatids from S phase until mitosis. To do so, cohesin must be protected against its cellular antagonist Wapl. Eco1 acetylates cohesin’s Smc3 subunit, which locks together the sister DNAs. We used yeast genetics to dissect how Wapl drives cohesin from chromatin and identified mutants of cohesin that are impaired in ATPase activity but remarkably confer robust cohesion that bypasses the need for the cohesin protectors Eco1 in yeast and Sororin in human cells. We uncover an unexpected functional asymmetry within the heart of cohesin’s highly conserved ABC-like ATPase machinery and show that an activity associated with one of cohesin’s two ATPase sites drives DNA release from cohesin rings. This key mechanism is conserved from yeast to humans. We propose that Eco1 locks cohesin rings around the sister chromatids by counteracting an asymmetric cohesin-associated ATPase activity.

2016-02-18 | GSE76891 | GEO

Glutamine methylation on Histone H2A is an RNA Polymerase I dedicated modification

Project description:Nucleosomes are decorated with numerous post-translational modifications capable of influencing many DNA processes. Here, we describe a new class of modification, methylation of glutamine, occurring on yeast histone H2A at position 105 (Q105) and human H2A at Q104. We identify Nop1 as the methyltransferase in yeast and we demonstrate that Fibrillarin is the equivalent enzyme in human cells. Glutamine methylation of H2A is restricted to the nucleolus. Global analysis in yeast, using a H2AQ105me specific antibody, show that this modification is exclusively enriched over the 35S rDNA transcriptional unit. We show that the Q105 residue is part of the binding site for the histone chaperone FACT (Facilitator of Transcription) complex. Methylation of Q105 or its substitution to alanine disrupts binding to FACT in vitro. A yeast strain mutated at Q105 exhibits a defect in histone incorporation and shows increased transcription at rDNA genes. This defect is phenocopied by mutations in FACT that decrease its activity. Together these data identify glutamine methylation of H2A as the first histone epigenetic mark dedicated to a specific RNA polymerase and define its function as a regulator of FACT interaction with nucleosomes.

2014-01-21 | E-MTAB-1447 | biostudies-arrayexpress

Mutations in cohesin-associated genes impair protein translation

Project description:The cohesin protein complex is well known for playing a role in chromosome segregation. However, it has additional less understood roles in transcription, DNA repair, and chromosome condensation. Mutants in two yeast orthologues (Eco1 and Scc2) of human cohesinopathy disease alleles were examined by transcriptional profiling in response to perturbation of the transcriptional program by amino acid starvation. Two cohesin mutants were compared to wt in a time course of amino acid starvation consisting of 4 time points, 3 replicates of each, for a total of 36 samples.

2011-04-01 | E-GEOD-27235 | biostudies-arrayexpress

Sister chromatid cohesion establishment by acetylation

Project description:Cohesion between sister chromatids depends on the chromosomal cohesin complex and allows the spindle apparatus in mitosis to recognize replicated chromosomes for segregation into daughter cells. Sister chromatid cohesion is established concomitant with DNA replication, and requires the essential Eco1 protein, a replication fork-associated acetyl transferase. The mechanism by which Eco1 establishes sister chromatid cohesion is not known. Here, we show that the cohesin subunit Smc3 is acetylated in an Eco1-dependent manner during S phase to establish sister chromatid cohesion. We isolated spontaneous suppressors of the thermosensitive eco1-1 allele in budding yeast, and identified the suppressor mutations from the hybridization pattern of genomic DNA on oligonucleotide tiling arrays. An acetylation mimicking mutation of a conserved lysine in Smc3 to asparagine (K113N) makes Eco1 dispensable for cell growth, indicating that Smc3 acetylation is Eco1’s only essential function. We identified a second set of eco1-1 suppressor mutations in the budding yeast ortholog of the cohesin regulator Wapl (Wpl1/Rad61). Wapl destabilizes cohesin on chromosomes, and Eco1-dependent Smc3 acetylation during S-phase might render cohesin resistant to Wapl. Our results clarify the role of Eco1 in the establishment of sister chromatid cohesion, and suggest that Eco1 modifies cohesin to stabilize an Eco1-independent cohesion establishment reaction.

2008-07-24 | GSE11527 | GEO

The Scc2NIPBL/Scc4MAU2 complex acts in sister chromatid cohesion and transcriptional regulation by maintaining nucleosome-free regions [ChIP-seq]

Project description:The Scc2/Scc4 complex binds to broad nucleosome-free regions in the promoters of highly expressed genes. The cohesin loader is recruited to these sites by the RSC chromatin remodeling complex ChIp- Sequencing analysis of the distribution of Scc2 and Scc4 on budding yeast chromosomes.An input sample was analysed as a control.

2014-08-01 | E-GEOD-56993 | biostudies-arrayexpress

Genomic targets sites of the Candida glabrata transcription factor Pdr1

Project description:Pdr1 is the major regulator of azole resistance in the fungal pathogen Candida glabrata. Earlier experiments demonstrated that expression of Pdr1 itself is increased when cells lose their mitochondrial genome (rho0). Here we use chromatin immunoprecipitation coupled with highthroughput sequencing (ChIP-seq) to map the genomic binding sites for Pdr1 in both normal and rho0 cells. These data provide the first look at genes that are likely to represent the direct targets of Pdr1 in this important pathogen. Examination of Pdr1 binding sites using two different antibodies in five different strains. Strains labeled TAP carry the TAP-tagged allele and capture was done with anti-TAP. The control was performed by carrying out a ChIP reaction on rho0 TAP-PDR1 cells but with no primary anti-TAP antibody. Since Pdr1 expression is the highest in this background, this was selected as the best control for antibody specificity. We also performed ChIP reactions on rho+, rho0 and cells lacking the PDR1 gene (pdr1D) cells using the anti-Pdr1 antibody. The control for these reactions was a ChIP experiment using anti-Pdr1 antibody on cells lacking the endogenous Pdr1 protein.

2014-09-12 | E-GEOD-59839 | biostudies-arrayexpress

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