Project description:We report the genome-wide analysis from chromatin immunoprecipitated DNA (ChIP-sequencing) of the DNA binding pattern of ParBF (SopB) of plasmid F. This study, performed in E. coli and Salmonella typhimurium, investigates the impact of DNA supercoiling on ParBF DNA binding profiles in vivo. We found that variation in DNA supercoiling does not significantly affect the ParB DNA binding profiles even on linear DNA.
Project description:DNA supercoiling is essential for life because it controls critical processes, including transcription, replication and recombination. Current methods to measure DNA supercoiling in vivo are laborious and unable to examine single cells. Here we report a method for high-throughput measurement of bacterial DNA supercoiling in vivo. Fluorescent Evaluation of DNA Supercoiling (FEDS) utilizes a plasmid harboring the gene for a green fluorescent protein transcribed by a discovered promoter that responds exclusively to DNA supercoiling, and the gene for a red fluorescent protein transcribed by a constitutive promoter as internal standard. Using FEDS, we uncovered single cell heterogeneity in DNA supercoiling and established that, surprisingly, population-level decreases in DNA supercoiling result from a low mean/high variance DNA supercoiling subpopulation, rather than a homogeneous shift in supercoiling of the whole population. In addition, we identified a regulatory loop in which a gene that decreases DNA supercoiling is transcriptionally repressed when DNA supercoiling increases.
Project description:DNA supercoiling is essential for all living cells because it controls all processes involving DNA. In bacteria, global DNA supercoiling results from the opposing activities of topoisomerase I, which relaxes DNA, and DNA gyrase, which compacts DNA. These enzymes are widely conserved, sharing >91% amino acid identity between the closely related species Escherichia coli and Salmonella enterica serovar Typhimurium. Why, then, do E. coli and Salmonella exhibit different DNA supercoiling when experiencing the same conditions? We now report that this surprising difference reflects disparate activation of their DNA gyrases by the polyamine spermidine and its precursor putrescine. In vitro, Salmonella DNA gyrase activity was sensitive to changes in putrescine concentration within the physiological range, whereas activity of the E. coli enzyme was not. In vivo, putrescine activated the Salmonella DNA gyrase and spermidine the E. coli enzyme. High extracellular Mg2+ decreased DNA supercoiling exclusively in Salmonella by reducing the putrescine concentration. Our results establish the basis for the differences in global DNA supercoiling between E. coli and Salmonella, define a signal transduction pathway regulating DNA supercoiling, and identify potential targets for antibacterial agents.
Project description:This study was designed to investigate DNA supercoiling across the human genome and to understand how supercoiling domains impact on higher levels of genome organisation. DNA supercoiling is an inherent consequence of twisting DNA and is critical for regulating gene expression and DNA replication. However, DNA supercoiling at a genomic scale in human cells is uncharacterized. To map supercoiling we used biotinylated-trimethylpsoralen as a DNA structure probe to show the genome is organized into supercoiling domains. Domains are formed and remodeled by RNA polymerase and topoisomerase activities and are flanked by GC-AT boundaries and CTCF binding sites. Under-wound domains are transcriptionally active, enriched in topoisomerase I, “open” chromatin fibers and DNaseI sites, but are depleted of topoisomerase II. Furthermore DNA supercoiling impacts on additional levels of chromatin compaction as under-wound domains are cytologically decondensed, topologically constrained, and decompacted by transcription of short RNAs. We suggest that supercoiling domains create a topological environment that facilitates gene activation providing an evolutionary purpose for clustering genes along chromosomes.
Project description:We studied the response to increased DNA-supercoiling in Streptococcus pneumoniae by using seconeolitsine (SCN), a DNA topoisomerase I inhibitor. A homeostatic transcriptional response allowing recovering of supercoiling density was observed in cells treated with subinhibitory SCN concentrations. Supercoiling increases up to 40.7% (6 µM SCN) and 72.9% (8 µM SCN) were reverted to 8.5% and 44.1%, respectively. Likewise, recovery of viability and DNA-supercoiling were observed when cells were treated with those SCN concentrations and the drug was removed. The main DNA topoisomerase gene affected was topA, whose transcription depended on the supercoiling level. A two stage global transcriptomic response with 8 µM seconeolitsine was detected. The early stage (5 and 15 min, 10% of the genome) represented a response induced by increased supercoiling. The second stage represented supercoiling recovery (30 min, 2.0% of the genome). Almost 25% of the early responsive genes formed clusters with coordinated transcriptional regulation. Twelve clusters were evident, with sizes of 6.7 to 31.4 Kb (9 to 22 responsive genes). Strikingly, clusters did not contradict those observed under DNA relaxation, suggesting that bacteria manage supercoiling stress using overlapping responses. This is the first study describing a global transcriptomic response triggered by an increase in DNA supercoiling in bacteria.
Project description:This study was designed to investigate DNA supercoiling across the human genome and to understand how supercoiling domains impact on higher levels of genome organisation. DNA supercoiling is an inherent consequence of twisting DNA and is critical for regulating gene expression and DNA replication. However, DNA supercoiling at a genomic scale in human cells is uncharacterized. To map supercoiling we used biotinylated-trimethylpsoralen as a DNA structure probe to show the genome is organized into supercoiling domains. Domains are formed and remodeled by RNA polymerase and topoisomerase activities and are flanked by GC-AT boundaries and CTCF binding sites. Under-wound domains are transcriptionally active, enriched in topoisomerase I, “open” chromatin fibers and DNaseI sites, but are depleted of topoisomerase II. Furthermore DNA supercoiling impacts on additional levels of chromatin compaction as under-wound domains are cytologically decondensed, topologically constrained, and decompacted by transcription of short RNAs. We suggest that supercoiling domains create a topological environment that facilitates gene activation providing an evolutionary purpose for clustering genes along chromosomes.
Project description:This study was designed to investigate DNA supercoiling across the human genome and to understand how supercoiling domains impact on higher levels of genome organisation. DNA supercoiling is an inherent consequence of twisting DNA and is critical for regulating gene expression and DNA replication. However, DNA supercoiling at a genomic scale in human cells is uncharacterized. To map supercoiling we used biotinylated-trimethylpsoralen as a DNA structure probe to show the genome is organized into supercoiling domains. Domains are formed and remodeled by RNA polymerase and topoisomerase activities and are flanked by GC-AT boundaries and CTCF binding sites. Under-wound domains are transcriptionally active, enriched in topoisomerase I, “open” chromatin fibers and DNaseI sites, but are depleted of topoisomerase II. Furthermore DNA supercoiling impacts on additional levels of chromatin compaction as under-wound domains are cytologically decondensed, topologically constrained, and decompacted by transcription of short RNAs. We suggest that supercoiling domains create a topological environment that facilitates gene activation providing an evolutionary purpose for clustering genes along chromosomes.
Project description:We studied the response to increased DNA-supercoiling in Streptococcus pneumoniae by using seconeolitsine (SCN), a DNA topoisomerase I inhibitor. A homeostatic transcriptional response allowing recovering of supercoiling density was observed in cells treated with subinhibitory SCN concentrations. Supercoiling increases up to 40.7% (6 µM SCN) and 72.9% (8 µM SCN) were reverted to 8.5% and 44.1%, respectively. Likewise, recovery of viability and DNA-supercoiling were observed when cells were treated with those SCN concentrations and the drug was removed. The main DNA topoisomerase gene affected was topA, whose transcription depended on the supercoiling level. A two stage global transcriptomic response with 8 µM seconeolitsine was detected. The early stage (5 and 15 min, 10% of the genome) represented a response induced by increased supercoiling. The second stage represented supercoiling recovery (30 min, 2.0% of the genome). Almost 25% of the early responsive genes formed clusters with coordinated transcriptional regulation. Twelve clusters were evident, with sizes of 6.7 to 31.4 Kb (9 to 22 responsive genes). Strikingly, clusters did not contradict those observed under DNA relaxation, suggesting that bacteria manage supercoiling stress using overlapping responses. This is the first study describing a global transcriptomic response triggered by an increase in DNA supercoiling in bacteria.
Project description:We studied the response to increased DNA-supercoiling in Streptococcus pneumoniae by using seconeolitsine (SCN), a DNA topoisomerase I inhibitor. A homeostatic transcriptional response allowing recovering of supercoiling density was observed in cells treated with subinhibitory SCN concentrations. Supercoiling increases up to 40.7% (6 µM SCN) and 72.9% (8 µM SCN) were reverted to 8.5% and 44.1%, respectively. Likewise, recovery of viability and DNA-supercoiling were observed when cells were treated with those SCN concentrations and the drug was removed. The main DNA topoisomerase gene affected was topA, whose transcription depended on the supercoiling level. A two stage global transcriptomic response with 8 µM seconeolitsine was detected. The early stage (5 and 15 min, 10% of the genome) represented a response induced by increased supercoiling. The second stage represented supercoiling recovery (30 min, 2.0% of the genome). Almost 25% of the early responsive genes formed clusters with coordinated transcriptional regulation. Twelve clusters were evident, with sizes of 6.7 to 31.4 Kb (9 to 22 responsive genes). Strikingly, clusters did not contradict those observed under DNA relaxation, suggesting that bacteria manage supercoiling stress using overlapping responses. This is the first study describing a global transcriptomic response triggered by an increase in DNA supercoiling in bacteria. RNA was extracted from S. pneumoniae R6 cultures during exponential growth, amplified and used for microarray hibridization. Two independent replicates were performed.
Project description:This study was designed to investigate DNA supercoiling across the human genome and to understand how supercoiling domains impact on higher levels of genome organisation. DNA supercoiling is an inherent consequence of twisting DNA and is critical for regulating gene expression and DNA replication. However, DNA supercoiling at a genomic scale in human cells is uncharacterized. To map supercoiling we used biotinylated-trimethylpsoralen as a DNA structure probe to show the genome is organized into supercoiling domains. Domains are formed and remodeled by RNA polymerase and topoisomerase activities and are flanked by GC-AT boundaries and CTCF binding sites. Under-wound domains are transcriptionally active, enriched in topoisomerase I, M-bM-^@M-^\openM-bM-^@M-^] chromatin fibers and DNaseI sites, but are depleted of topoisomerase II. Furthermore DNA supercoiling impacts on additional levels of chromatin compaction as under-wound domains are cytologically decondensed, topologically constrained, and decompacted by transcription of short RNAs. We suggest that supercoiling domains create a topological environment that facilitates gene activation providing an evolutionary purpose for clustering genes along chromosomes. The binding of bTMP, as a reporter for DNA supercoiling, was investigated in RPE1 cells. Experiments were biological replicates