Replisomes restrict SMC translocation in vivo
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PROVIDER: PRJNA1188612 | ENA |
REPOSITORIES: ENA
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Project description:Structural maintenance of chromosomes (SMC) complexes organize genomes by extruding DNA loops. How collisions between SMC complexes and DNA polymerases are resolved in vivo remains poorly understood. Taking advantage of the ability to load SMC complexes at defined sites in the Bacillus subtilis genome, we investigated this problem. We engineered head-on and head-to-tail collisions between SMC complexes and the replisome, and monitored SMC translocation by time-resolved ChIP-seq and Hi-C and replisome progression by marker frequency analysis. We report that SMC complexes do not affect replication progression. By contrast, the replisome blocks SMC translocation regardless of collision orientation. Combining experimental data with simulations, we determined that SMC is first blocked by the replisome and then released from the chromosome. However, occasionally SMC can bypass the replisome and continue translocating. Our findings establish that the replisome is a barrier to SMC-mediated DNA-loop extrusion, with implications for chromosome organization in all organisms.
2025-07-07 | GSE282455 | GEO
Project description:SMC translocation is unaffected by an excess of nucleoid associated proteins in vivo
| PRJNA1123659 | ENA
Project description:Genome organization is important for DNA replication, gene expression, and chromosome segregation. In bacteria, two large family of proteins, nucleoid-associated proteins (NAPs) and the SMC complexes, play important roles organizing the genome. NAPs are abundant DNA-binding proteins that can bend, wrap, bridge and compact DNA, while SMC complexes load on the chromosome, translocate on the DNA, and extrude DNA loops. How SMC loop extrusion is influenced by various NAPs remains unknown. In this study, we expressed a collection of representative prokaryotic chromosome-associated proteins in Bacillus subtilis, which introduce distinct DNA structures and pose different challenges for SMC loop extrusion. By fluorescence microscopy and chromatin immunoprecipitation experiments, we observed that these proteins bound to the genome in characteristic manners. Through genome-wide chromosome conformation capture assays, we found that the SMC complex can traverse these DNA-binding proteins without slowing down. Our findings reveal that the DNA loop extrusion activity of the SMC complex is unaffected by the chromosome-associated proteins and highlight the robustness of SMC motors on the busy chromatin.
2025-01-17 | GSE269767 | GEO
Project description:Structural maintenance of chromosomes (SMC) complexes shape the genomes of virtually all organisms but how they function remains incompletely understood. Recent studies in bacteria and eukaryotes have led to a unifying model in which these ring-shaped ATPases act along contiguous DNA segments processively enlarging DNA loops. In support of this model, single-molecule imaging experiments indicate that Saccharomyces cerevisiae condensin complexes can extrude DNA loops in an ATP hydrolysis dependent manner in vitro. Here, using time-resolved high-throughput chromosome conformation capture (Hi-C) we investigate the interplay between ATPase activity of the Bacillus subtilis SMC complex and loop formation in vivo. We show that point mutants in the SMC nucleotide binding domain that impair but do not eliminate ATPase activity not only exhibit delays in de novo loop formation but also have reduced rates of processive loop enlargement. These data provide in vivo evidence that SMC complexes function as loop extruders.
2018-08-09 | GSE95137 | GEO
Project description:Chromosome organization by structural maintenance of chromosomes (SMC) complexes is vital to living organisms. SMC complexes were recently found to be motors that extrude DNA loops. However, it remains unclear what happens when multiple complexes encounter one another in vivo on the same DNA and how interactions help organize an active genome. We created a crash-course track system to study SMC complex encounters in vivo by engineering the Bacillus subtilis chromosome to have defined SMC loading sites. Chromosome conformation capture (Hi-C) analyses of over 20 engineered strains show an amazing variety of never-before-seen chromosome folding patterns. Via 3D polymer simulations and theory, we find that these patterns require SMC complexes to bypass each other in vivo, as recently seen in an in vitro study. We posit that the bypassing activity enables SMC complexes to spatially organize a functional and busy genome.
2021-06-10 | GSE155279 | GEO
Project description:Smc/ScpAB promotes chromosome segregation in prokaryotes, presumably by compacting and resolving nascent sister chromosomes. The underlying mechanisms, however, are poorly understood. Here, we investigate the role of the Smc ATPase activity in the recruitment of Smc/ScpAB to the Bacillus subtilis chromosome. We demonstrate that targeting of Smc/ScpAB to ParB/parS loading sites is strictly dependent on engagement of Smc head domains and relies on an open organization of the Smc coiled coils. We find that dimerization of the Smc hinge domain stabilizes closed Smc rods and hinders head engagement as well as chromosomal targeting. Conversely, the ScpAB sub-complex promotes head engagement and Smc rod opening and thereby facilitates recruitment of Smc to parS sites. Upon ATP hydrolysis, Smc/ScpAB is released from loading sites and relocates within the chromosomeâpresumably through translocation along DNA double helices. Our findings define an intermediate state in the process of chromosome organization by Smc. ChIP-Seq experiments were performed on wild type and mutant cells of Bacillus subtilis 1A700.
2016-02-18 | E-GEOD-76949 | biostudies-arrayexpress
Project description:The Structural Maintenance of Chromosomes (SMC) complex plays an important role in chromosome organization and segregation in most living organisms. In Caulobacter crescentus, SMC is required to align the left and the right arms of the chromosome that run in parallel down the long axis of the cell. However, the mechanism of SMC-mediated alignment of chromosomal arms remains elusive. Here, using genome-wide methods and microscopy of single cells, we show that Caulobacter SMC is recruited to the centromeric parS site and that SMC-mediated arm alignment depends on the chromosome partitioning protein ParB. We provide evidence that SMC likely tethers the parS-proximal regions of the chromosomal arms together, promoting arm alignment. Furthermore, we show that highly-transcribed genes near parS that are oriented against SMC translocation disrupt arm alignment, suggesting that head-on transcription interferes with SMC translocation. Our results demonstrate a tight interdependence of bacterial chromosome organization and global patterns of transcription.
2017-07-23 | GSE97330 | GEO
Project description:SMC complexes are widely conserved ATP-powered loop extrusion motors indispensable for the faithful segregation of chromosomes during cell division. How SMC complexes translocate along DNA for loop extrusion and what happens when two complexes meet on the same DNA molecule is largely unknown. Revealing the origins and the consequences of SMC encounters is crucial for understanding the folding process not only of bacterial, but also of eukaryotic chromosomes. Here, we uncover several factors that influence bacterial chromosome organization by modulating the probability of such clashes. These factors include the number, the strength and the distribution of Smc loading sites, the residence time on the chromosome, the translocation rate, and the cellular abundance of Smc complexes. By studying various mutants, we show that these parameters are fine-tuned to reduce the frequency of encounters between Smc complexes, presumably as a risk mitigation strategy. Mild perturbations hamper chromosome organization by causing Smc collisions, implying that the cellular capacity to resolve them is rather limited. Altogether, we identify mechanisms that help to avoid Smc collisions and their resolution by Smc traversal or other potentially risky molecular transactions.
2021-07-30 | GSE163573 | GEO
Project description:Smc/ScpAB promotes chromosome segregation in prokaryotes, presumably by compacting and resolving nascent sister chromosomes. The underlying mechanisms, however, are poorly understood. Here, we investigate the role of the Smc ATPase activity in the recruitment of Smc/ScpAB to the Bacillus subtilis chromosome. We demonstrate that targeting of Smc/ScpAB to ParB/parS loading sites is strictly dependent on engagement of Smc head domains and relies on an open organization of the Smc coiled coils. We find that dimerization of the Smc hinge domain stabilizes closed Smc rods and hinders head engagement as well as chromosomal targeting. Conversely, the ScpAB sub-complex promotes head engagement and Smc rod opening and thereby facilitates recruitment of Smc to parS sites. Upon ATP hydrolysis, Smc/ScpAB is released from loading sites and relocates within the chromosome—presumably through translocation along DNA double helices. Our findings define an intermediate state in the process of chromosome organization by Smc.
2016-02-18 | GSE76949 | GEO
Project description:DNA-loop extruding SMC complexes can traverse one another in vivo
| PRJNA649231 | ENA