Topoisomerase function in E. coli replication fork movement
Ontology highlight
ABSTRACT:
ORGANISM(S): Escherichia coli
PROVIDER: GSE8 | GEO | 2001/07/30
SECONDARY ACCESSION(S): PRJNA85459
REPOSITORIES: GEO
Similar Datasets
Project description:Analysis of topoisomerase function in bacterial replication fork movement: use of DNA microarrays. We used DNA microarrays of the Escherichia coli genome to trace the progression of chromosomal replication forks in synchronized cells. We found that both DNA gyrase and topoisomerase IV (topo IV) promote replication fork progression. When both enzymes were inhibited, the replication fork stopped rapidly. The elongation rate with topo IV alone was 1/3 of normal. Genetic data confirmed and extended these results. Inactivation of gyrase alone caused a slow stop of replication. Topo IV activity was sufficient to prevent accumulation of (+) supercoils in plasmid DNA in vivo, suggesting that topo IV can promote replication by removing (+) supercoils in front of the chromosomal fork. This study is detailed in Khodursky AB et al.(2000) Proc Natl Acad Sci U S A 97:9419-24 Keywords: other
2001-07-30 | E-GEOD-8 | biostudies-arrayexpress
Project description:When DNA is unwound during replication, it becomes overtwisted and forms positive supercoils in front of the translocating DNA polymerase. Unless removed or dissipated, this superhelical tension can impede replication elongation. Topoisomerases, including gyrase and topoisomerase IV in bacteria, are required to relax positive supercoils ahead of DNA polymerase, but may not be sufficient for replication. Here, we find that GapR, a chromosome structuring protein in Caulobacter crescentus, is required to complete DNA replication. GapR associates in vivo with positively supercoiled chromosomal DNA, and our biochemical and structural studies demonstrate that GapR forms a dimer-of-dimers that fully encircles overtwisted DNA. Further, we show that GapR stimulates gyrase and topo IV to relax positive supercoils, thereby enabling DNA replication. Analogous chromosome structuring proteins that locate to the overtwisted DNA in front of replication forks may be present in other organisms, similarly helping to recruit and stimulate topoisomerases during DNA replication.
2018-09-13 | GSE100657 | GEO
Project description:DNA gyrase is an essential enzyme whose activity is required for DNA replication and chromosome maintenance. Inhibition of gyrase results in multiple physiological effects including changes in DNA superhelicity, replication arrest and DNA damage. Using genetic, genomic, statistical and biochemical techniques, we have untangled the contribution of individual effects, assessed their relative significance and concluded that: i) DNA replication is required for the formation of spatial transcriptional domains; ii) transcriptional response to gyrase inhibition is coordinated between at least two modules involved in DNA maintenance, relaxation and damage response; iii) genes whose transcriptional response to gyrase inhibition does not depend on the activity of topoisomerase I can be classified on the basis of the GC excess in their upstream and coding sequences into, respectively, activated and repressed by gyrase inhibition; iv) relaxation by topoisomerase I dominates the transcriptional response upon gyrase inhibition, followed by the effects of replication and RecA. Keywords: time course
2006-03-10 | GSE4408 | GEO
Project description:In many eukaryotes, Argonaute proteins, guided by short RNA sequences, defend cells against transposons and viruses. In the eubacterium Thermus thermophilus, the DNA-guided Argonaute TtAgo defends against transformation by DNA plasmids. Here, we report that TtAgo also participates in DNA replication. In vivo, TtAgo binds 15-18 nt DNA guides derived from the chromosomal region where replication terminates and associates with proteins known to act in DNA replication. When gyrase, the sole T. thermophilus type II topoisomerase, is inhibited, TtAgo allows the bacterium to finish replicating its circular genome. In contrast, loss of both gyrase and TtAgo activity slows growth and produces long sausage-like filaments in which the individual bacteria are linked by DNA. Finally, wild-type T. thermophilus outcompetes an otherwise isogenic strain lacking TtAgo. We propose that the primary role of TtAgo is to help T. thermophilus disentangle the catenated circular chromosomes generated by DNA replication.
2020-03-17 | MSV000085109 | MassIVE
Project description:Type II topoisomerases (topos) are a ubiquitous and essential class of enzymes that form transient enzyme-bound double-stranded breaks on DNA called cleavage complexes. The location and frequency of these cleavage complexes on DNA is important for cellular function, genomic stability, and a number of clinically important anticancer and antibacterial drugs, e.g., quinolones. We developed a simple high-accuracy end-sequencing (SHAN-seq) method to sensitively map type II topo cleavage complexes on DNA in vitro. Using SHAN-seq, we detected Escherichia coli gyrase and topoisomerase IV cleavage complexes at hundreds of sites on supercoiled pBR322 DNA, approximately one site every ten bp, with frequencies that varied by two-to-three orders of magnitude. These sites included previously identified sites and 20-50 fold more new sites. We show that the location and frequency of cleavage complexes at these sites are enzyme-specific and vary substantially in the presence of the quinolone, ciprofloxacin, but not with DNA supercoil chirality, i.e., negative vs. positive supercoiling. SHAN-seq’s exquisite sensitivity provides an unprecedented single-nucleotide resolution view of the distribution of gyrase and topoisomerase IV cleavage complexes on DNA. Moreover, the discovery that these enzymes can cleave DNA at orders of magnitude more sites than the relatively few previously known sites resolves the apparent paradox of how these enzymes resolve topological problems throughout the genome.
2024-08-06 | GSE267149 | GEO
Project description:During chromosome duplication the parental DNA molecule becomes over-wound, or positively supercoiled, in the region ahead of the advancing replication fork. To allow fork progression this superhelical tension has to be removed by topoisomerases, which operate by introducing transient DNA breaks. Positive supercoiling can also be diminished if the advancing fork rotates along the DNA helix, but then sister chromatid intertwinings form in its wake. Despite these insights it remains largely unknown how replicationinduced superhelical stress is dealt with on linear, eukaryotic chromosomes. Here we show that this stress increases with the length of budding yeast chromosomes. This opens for the possibility that superhelical tension is handled on a chromosome scale and not only within topologically closed chromosomal domains as the current view predicts. We found that inhibition of type I topoisomerases leads to a late replication delay of longer, but not shorter chromosomes. This phenotype is also displayed by cells expressing mutated versions of the cohesin- and condensin–related Smc5/6 complex. The chromosomal association of the Smc5/6 complex is shown to increase in response to chromosome lengthening, chromosome circularization, or inactivation of Topoisomerase 2, all having the potential to increase the number of sister chromatid intertwinings 3. Furthermore, non-functional Smc6 reduces the accumulation of intertwined sister plasmids after one round of replication in the absence of Topoisomerase 2 function. Our results demonstrate that the length of a chromosome influences the need of superhelical tension release in Saccharomyces cerevisiae, and allow us to propose a model where the Smc5/6 complex facilitates fork rotation by sequestering nascent chromatid intertwinings which form behind the replication machinery. Smc6、Nse4, and Scc2 profiles with or without topological tension was analyzed (in top2 mutant, cells with circular chromosome, and fragmented chromosome) . 17 ChIP samples and corresponding WCE fractions have been analyzed.
2011-02-28 | E-GEOD-26263 | biostudies-arrayexpress
Project description:[original title] Chromosome replication initiates at multiple replicons and terminates when forks converge. In Escherichia coli, the Tus-TER complex mediates polar fork converging at the terminator region and aberrant termination events challenge chromosome integrity and segregation. Since in eukaryotes termination is less characterized, we used budding yeast to identify the factors assisting fork fusion at replicating chromosomes. Using genomic and mechanistic studies we have identified and characterized 71 chromosomal termination regions (TERs). TERs contain fork pausing elements that influence fork progression and merging. The Rrm3 DNA helicase assists fork progression across TERs counteracting the accumulation of X-shaped structures. The Top2 DNA topoisomerase associates at TERs in S-phase and G2/M facilitates fork fusion and prevents DNA breaks and genome rearrangements at TERs. We propose that in eukaryotes replication fork barriers, Rrm3 and Top2 coordinate replication fork progression and fusion at termination regions thus counteracting abnormal genomic transitions. Signal tracks in BED format suitable for visualization on the UCSC genome browser can be found at http://bio.ifom-ieo-campus.it/supplementary/Fachinetti_et_al_MOLCELL_2010
2010-08-28 | GSE19061 | GEO
Project description:The fidelity of DNA replication is governed by a network of DNA repair mechanisms. Defects in replication fork protection can fuel genome instability in cancer, while also creating cancer-specific vulnerabilities. Here, we provide a comprehensive proteomic characterization of the replication fork response to topoisomerase 1 inhibition, a widely used mainstay chemotherapy. We reveal profound changes in the fork proteome and chromatin environment in response to seDSBs and topological stress, and classify fork repair factors according to their specificity for broken and stalled forks. These distinct fork responses also oppositely affect nucleosome occupancy and nuclear membrane interactions. ATM inhibition dramatically rewired the fork breakage response, revealing that ATM promotes HR-dependent fork restart by concomitantly promoting DNA-end resection and suppressing DSB associated protein ubiquitination and NHEJ. Together, this collection of damaged fork proteomes provides an ample resource to understand fork repair mechanisms and identify druggable targets and novel cancer vulnerabilities.
2021-01-15 | PXD018092 | Pride
Project description:During chromosome duplication the parental DNA molecule becomes over-wound, or positively supercoiled, in the region ahead of the advancing replication fork. To allow fork progression this superhelical tension has to be removed by topoisomerases, which operate by introducing transient DNA breaks. Positive supercoiling can also be diminished if the advancing fork rotates along the DNA helix, but then sister chromatid intertwinings form in its wake. Despite these insights it remains largely unknown how replicationinduced superhelical stress is dealt with on linear, eukaryotic chromosomes. Here we show that this stress increases with the length of budding yeast chromosomes. This opens for the possibility that superhelical tension is handled on a chromosome scale and not only within topologically closed chromosomal domains as the current view predicts. We found that inhibition of type I topoisomerases leads to a late replication delay of longer, but not shorter chromosomes. This phenotype is also displayed by cells expressing mutated versions of the cohesin- and condensin–related Smc5/6 complex. The chromosomal association of the Smc5/6 complex is shown to increase in response to chromosome lengthening, chromosome circularization, or inactivation of Topoisomerase 2, all having the potential to increase the number of sister chromatid intertwinings 3. Furthermore, non-functional Smc6 reduces the accumulation of intertwined sister plasmids after one round of replication in the absence of Topoisomerase 2 function. Our results demonstrate that the length of a chromosome influences the need of superhelical tension release in Saccharomyces cerevisiae, and allow us to propose a model where the Smc5/6 complex facilitates fork rotation by sequestering nascent chromatid intertwinings which form behind the replication machinery.
2011-02-28 | GSE26263 | GEO
Project description:Replication forks temporarily or terminally pause at hundreds of hard-to-replicate regions around the genome. A conserved pair of budding yeast replisome components Tof1-Csm3 (fission yeast Swi1-Swi3 and human TIMELESS-TIPIN) acts as a ‘molecular brake’ and promotes fork slowdown at proteinaceous replication fork barriers (RFBs), while the accessory helicase Rrm3 assists the replisome in removing protein obstacles. Here we show that Tof1-Csm3 complex promotes fork pausing independently of Rrm3 helicase by recruiting topoisomerase I (Top1) to the replisome. Topoisomerase II (Top2) partially compensates for the pausing decrease in cells when Top1 is lost from the replisome. The C-terminus of Tof1 is specifically required for Top1 recruitment to the replisome and fork pausing but not for DNA replication checkpoint (DRC) activation. We propose that forks pause at proteinaceous RFBs through a ‘sTOP’ mechanism (‘slowing down with TOPoisomerases I-II’), which we show also contributes to protecting cells from topoisomerase-blocking agents.
2019-11-07 | GSE140034 | GEO