Global spatial organization of γ proteobacterial nucleoids is determined by specific long-range interactions (E. coli)
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ABSTRACT:
ORGANISM(S): Escherichia coli
PROVIDER: GSE40603 | GEO | 2013/05/02
SECONDARY ACCESSION(S): PRJNA174425
REPOSITORIES: GEO
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Project description:GCC was used to determine the structure of E. coli grown in LB or treated with SHX. The bacterial genome is highly condensed into a nucleoid structure. Here we present global analyses of the genome spatial organization for two M-NM-3-proteobacteria: Escherichia coli and Pseudomonas aeruginosa by Genome Conformation Capture. Long distance interactions occurred within the E. coli and P. aeruginosa nucleoids with frequencies that were affected by growth condition and gene dosage. Spatial clustering of genes that are either up or down-regulated depended on the environmental signals, indicating a non-random functional organization of the nucleoid. The largest changes in gene expression upon amino acid starvation occurred in genes that participate in long-range interactions. These genes remained highly spatially clustered when transcript levels decreased. Environment specific interactions were related to DNA motifs but did not correlate with binding sites for nucleoid associated proteins. Overall we identify spatial organization as a significant factor in bacterial gene regulation and suggest that the prokaryotic operon is not simply a linear entity. 4 samples grown in LB; 4 samples treated with SHX. For Genome Conformation Capture (GCC) analyses, E. coli strains were recovered from -80M-BM-0C on LB agar (2%) plates for 24 hours. LB medium (3ml) starter cultures were inoculated and grown (37M-BM-0C, 220rpm, 16h). The Optical Density (OD600) of cultures was measured and used to inoculate LB test cultures to an OD600 of ~0.02. The test cultures were grown (37M-BM-0C, 220rpm) until the OD600 reached ~0.25 and then harvested. For the serine hydroximate (SHX) treated samples the cultures were treated with SHX (500 M-BM-5g/ml, 30 min) before harvesting. E. coli chromatin was prepared according to Rodley et al. (2009)with the following modifications. A total of 5*109 cells were cross-linked with formaldehyde (1% final v/v, 20min, RT) and then quenched with glycine (125mM final, 10min). Cells were collected by centrifugation (4000rpm, 15min, 4M-BM-0C), washed twice (1% PBS, 1% TritonX-100, 5ml/50ml culture) and pelleted (4000rpm, 15min, 4M-BM-0C). Cell pellets were suspended in 800M-NM-<l of B1 lysis buffer (10mM Tris pH 8.0, 50mM NaCl, 10mM EDTA, 20% (w/v) sucrose, 1mg/ml lysozyme) and incubated (37M-BM-0C, 30min). 800M-NM-<l of B2 lysis buffer (200mM Tris pH 8.0, 600mM NaCl, 4% TritonX-100, 1 protease inhibitor tablet (Roche) per 10ml of buffer added just before use) was gently added, mixed by inversion 3-4 times and incubated (37M-BM-0C, 10min). The cell lysate was centrifuged (21,500g, 20min, 4M-BM-0C) and the supernatant decanted. The chromatin was washed once with 1ml of chromatin digestion buffer (10mM Tris-HCl pH 8.0, 5mM MgCl2, 0.1% TritonX-100) by inverting the tube 3-4 times and centrifuged (21,500g, 20min, 4M-BM-0C). The supernatant was decanted and the chromatin pellet was suspended in 500M-NM-<l chromatin digestion buffer. Chromatin samples were aliquoted into 10 sets of 5*108 cells. Samples were digested with HhaI (100U, New England Biolabs). Following digestion a ligation control was added and the samples were ligated with T4 DNA ligase (20U, Invitrogen). Following ligation, cross-links were removed in the presence of proteinase K (0.45U, Fermentas). RNA was removed and pUC19 plasmid (27.4pg/2ml) was added as a sequencing control prior to three extractions with 1:1 Phenol:Chloroform. DNA was column purified (Zymo, DNA clean and concentratorTM-5 kit) according to the manufacturerM-bM-^@M-^Ys instructions and eluted in milliQ H2O before combining for sequencing. 3M-NM-<g of purified DNA was sent for pared-end sequencing at the ATC sequencing facility (Rockville, MD, USA) on an Illumina Hi-Seq. External ligation controls were produced by PCR amplification of short regions from the Lambda phage genome and the pRS426. Primers (Table S4 were designed to include an HhaI site at one end of the final product. PCR products were purified using a PCR purification kit (Qiagen), digested with HhaI (4U, 37M-BM-0C, 2h) and purified again. Purified, digested PCR products were introduced into the GCC samples at a 1:1 ratio with the number of genomes prior to the ligation step during GCC preparation. The pRS426 fragment was introduced into the exponential phase (LB grown) samples and resulted in 220 separate ligation events with HhaI restriction fragments on the genome. The Lambda phage fragment was introduced into the SHX treated samples and resulted in 2 ligation events with HhaI fragments on the genome. Network assembly was performed using the Topography suite v1.19. GCC networks were constructed from 100bp (E. coli) paired end Illumina Genome Analyser sequence reads. Topography uses the SOAP algorithm to position PE tags and single ends which contain a HhaI (E. coli) restriction site onto the E. coli (NC_000913) reference genomes, respectively. Each reference genome also contained the pUC19 (SYNPUC19CV) sequence. For the E. coli alignment the sequences of the pRS426 plasmid and Lambda phage ligation controls were also included in the file to which the sequences were aligned. No mismatches or unassigned bases (N) were allowed during positioning. Except where indicated, bioinformatics and statistical analyses were performed on interactions in which the sequence reads were able to be mapped uniquely onto the reference genome and were above the FDR cut-off value (5). All bioinformatics analysis was perfumed using in house Perl scripts.
2013-05-02 | E-GEOD-40603 | biostudies-arrayexpress
Project description:To fit within the confines of the cell, bacterial chromosomes are highly condensed into a structure called the nucleoid. Despite the high degree of compaction in the nucleoid, the genome remains accessible to essential biological processes, such as replication and transcription. Here, we present the first high-resolution chromosome conformation capture-based molecular analysis of the spatial organization of the Escherichia coli nucleoid during rapid growth in rich medium and following an induced amino acid starvation that promotes the stringent response. Our analyses identify the presence of origin and terminus domains in exponentially growing cells. Moreover, we observe an increased number of interactions within the origin domain and significant clustering of SeqA-binding sequences, suggesting a role for SeqA in clustering of newly replicated chromosomes. By contrast, ‘histone-like’ protein (i.e. Fis, IHF and H-NS) binding sites did not cluster, and their role in global nucleoid organization does not manifest through the mediation of chromosomal contacts. Finally, genes that were downregulated after induction of the stringent response were spatially clustered, indicating that transcription in E. coli occurs at transcription foci. A 4 chips study of exponentially growing wild type E. coli strain MG1655 grown in LB rich media or after induction of the stringent response by serine hydroxamate for 30 min. Two technical replicates, Three biological replicates mixed prior hybridization on the chip.
2013-05-01 | E-GEOD-40304 | biostudies-arrayexpress
Project description:To fit within the confines of the cell, bacterial chromosomes are highly condensed into a structure called the nucleoid. Despite the high degree of compaction in the nucleoid, the genome remains accessible to essential biological processes, such as replication and transcription. Here, we present the first high-resolution chromosome conformation capture-based molecular analysis of the spatial organization of the Escherichia coli nucleoid during rapid growth in rich medium and following an induced amino acid starvation that promotes the stringent response. Our analyses identify the presence of origin and terminus domains in exponentially growing cells. Moreover, we observe an increased number of interactions within the origin domain and significant clustering of SeqA-binding sequences, suggesting a role for SeqA in clustering of newly replicated chromosomes. By contrast, ‘histone-like’ protein (i.e. Fis, IHF and H-NS) binding sites did not cluster, and their role in global nucleoid organization does not manifest through the mediation of chromosomal contacts. Finally, genes that were downregulated after induction of the stringent response were spatially clustered, indicating that transcription in E. coli occurs at transcription foci.
2013-05-01 | GSE40304 | GEO
Project description:Nucleoid remodeling facilitated by DNA supercoiling results in changes in nucleoid configuration and involves nucleoid-associated proteins (NAPs) and structural maintenance of chromosomes (SMC) proteins among others. Changes in nucleoid configurations regulated by NAPs are synchronized with cellular adaptation and influence the simultaneous expression of several genes. HU, a ubiquitous bacterial histone-like protein, is among the most conserved and abundant NAPs in eubacteria. In Escherichia coli, HU forms dimers by HUα self-association (HUαα) or by HUα-HUβ interactions (HUαβ). HUα is mostly expressed during lag and early exponential growth phase and HUβ is expressed only during the later exponential and stationary phase, pointing to distinct HUαα/DNA and HUαβ/DNA packaging of the nucleoid in regulating expression patterns during growth and stasis. Mutations or the deletion of HU transform the E. coli nucleoid to a different form and alter overall transcription program; thus, HU interactions with DNA directly affect global gene regulation. Recently, analysis of high-resolution contact maps of the E. coli nucleoid revealed an important role of HU to promote long-range DNA-DNA contacts within the nucleoid. Yet, the molecular connections between HU-DNA interactions and changes in nucleoid architecture that regulate gene expression globally remain unknown. Here, we explored the higher-order E. coli nucleoid organization by soft x-ray tomography (SXT) and revealed an effect of HU surface charges in overall nucleoid organization and rearrangements. We also studied global transcription by next-generation RNA sequencing (RNA-Seq) and found a link between nucleoid rearrangement and changes in global transcription. To determine the functional relationships of observed nucleoid rearrangement and HU-DNA interactions, we also characterized the overall organization of HU nucleoprotein complexes in solution by small angle x-ray scattering (SAXS). We found that HUαα-mediated DNA networks are different at different ionic strengths and pHs. By means of macromolecular crystallography, we additionally elucidate HUαα dependent molecular switches that modulate DNA networking. This integrative structural study explains how HUαα regulates dynamic transformations of the nucleoid by DNA bridging to control nucleoid rearrangement and global gene regulation.
2020-04-01 | GSE134667 | GEO
Project description:GCC was used to determine the response of P. aeruginosa nucleoid structure to different environmental conditions.
2016-11-02 | GSE40353 | GEO
Project description:Autoantibodies against nucleic acids and excessive type I Interferon (IFN) are hallmarks of human Systemic Lupus Erythematosus (SLE). We previously reported that SLE neutrophils, exposed to TLR7-agonist autoantibodies, release interferogenic DNA, which we now demonstrate to be of mitochondrial origin. We further show that healthy human neutrophils do not complete mitophagy upon induction of mitochondrial damage. Rather, they extrude mitochondrial components, including DNA (mtDNA), devoid of oxidized residues. When MtDNA undergoes oxidation, it is directly routed to lysosomes for degradation. This rerouting requires dissociation from the transcription factor TFAM, a dual high mobility group (HMG) protein involved in maintenance and compaction of the mitochondrial genome into nucleoids. Exposure of SLE neutrophils, or healthy IFNprimed neutrophils, to anti-RNP autoantibodies blocks TFAM phosphorylation, a necessary step for nucleoid dissociation. Consequently, oxidized nucleoids accumulate within mitochondria and are eventually extruded as potent interferogenic complexes. In support of the in vivo relevance of this phenomenon, mitochondrial retention of oxidized nucleoids is a feature of SLE blood neutrophils, and autoantibodies against oxidized mtDNA are present in a fraction of patients. This pathway represents a novel therapeutic target in human SLE. 4 samples, no replicates, 2 controls. 2 samples are Neutrophils cultured with and without CCCP (control). 2 samples are Monocytes cultured with and without CCCP (control).
2016-04-07 | E-GEOD-78243 | biostudies-arrayexpress
Project description:Autoantibodies against nucleic acids and excessive type I Interferon (IFN) are hallmarks of human Systemic Lupus Erythematosus (SLE). We previously reported that SLE neutrophils, exposed to TLR7-agonist autoantibodies, release interferogenic DNA, which we now demonstrate to be of mitochondrial origin. We further show that healthy human neutrophils do not complete mitophagy upon induction of mitochondrial damage. Rather, they extrude mitochondrial components, including DNA (mtDNA), devoid of oxidized residues. When MtDNA undergoes oxidation, it is directly routed to lysosomes for degradation. This rerouting requires dissociation from the transcription factor TFAM, a dual high mobility group (HMG) protein involved in maintenance and compaction of the mitochondrial genome into nucleoids. Exposure of SLE neutrophils, or healthy IFNprimed neutrophils, to anti-RNP autoantibodies blocks TFAM phosphorylation, a necessary step for nucleoid dissociation. Consequently, oxidized nucleoids accumulate within mitochondria and are eventually extruded as potent interferogenic complexes. In support of the in vivo relevance of this phenomenon, mitochondrial retention of oxidized nucleoids is a feature of SLE blood neutrophils, and autoantibodies against oxidized mtDNA are present in a fraction of patients. This pathway represents a novel therapeutic target in human SLE.
2016-04-07 | GSE78243 | GEO
Project description:As in Eukaryotes, bacterial genomes are not randomly folded. Bacterial genetic information is generally carried on a circular chromosome with a single origin of replication from which two replication forks proceed bidirectionaly towards the opposite terminus region. Here we investigate the higher-order architecture of the Escherichia coli genome, showing its partition into two structuraly distinct entities by a complex and intertwined network of contacts: the replication terminus (ter) region and the rest of the chromosome. Outside ter, the condensin MukBEF and the ubiquitous nucleoid-associated protein (NAP) HU promote DNA contacts in the megabase range. Within ter, the MatP protein prevents MukBEF activity and contacts are restricted to ~280 kb creating a domain with distinct structural properties. We also show how other NAPs contribute to nucleoid organization, such as H-NS that restricts short-range interactions. Combined, these results reveal the contributions of major, evolutionary conserved proteins in a bacterial chromosome organization.
2017-12-07 | GSE107301 | GEO
Project description:Global spatial organization of γ proteobacterial nucleoids is determined by specific long-range interactions (E. coli)
| PRJNA174425 | ENA
Project description:Global spatial organization of γ proteobacterial nucleoids is determined by specific long-range interactions.
| PRJNA173653 | ENA