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XerD unloads bacterial SMC complexes at the replication terminus.

ABSTRACT: Bacillus subtilis structural maintenance of chromosomes (SMC) complexes are topologically loaded at centromeric sites adjacent to the replication origin by the partitioning protein ParB. These ring-shaped ATPases then translocate down the left and right chromosome arms while tethering them together. Here, we show that the site-specific recombinase XerD, which resolves chromosome dimers, is required to unload SMC tethers when they reach the terminus. We identify XerD-specific binding sites in the terminus region and show that they dictate the site of unloading in a manner that depends on XerD but not its catalytic residue, its partner protein XerC, or the recombination site dif. Finally, we provide evidence that ParB and XerD homologs perform similar functions in Staphylococcus aureus. Thus, two broadly conserved factors that act at the origin and terminus have second functions in loading and unloading SMC complexes that travel between them.

SUBMITTER: Karaboja X

PROVIDER: S-EPMC7897262 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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XerD unloads bacterial SMC complexes at the replication terminus.

Karaboja Xheni X Ren Zhongqing Z Brandão Hugo B HB Paul Payel P Rudner David Z DZ Wang Xindan X

Molecular cell 20210119 4

Bacillus subtilis structural maintenance of chromosomes (SMC) complexes are topologically loaded at centromeric sites adjacent to the replication origin by the partitioning protein ParB. These ring-shaped ATPases then translocate down the left and right chromosome arms while tethering them together. Here, we show that the site-specific recombinase XerD, which resolves chromosome dimers, is required to unload SMC tethers when they reach the terminus. We identify XerD-specific binding sites in the ...[more]

PMID: 33472056

Similar Datasets

XerD is required to unload bacterial SMC complexes at the replication terminus

Project description:Bacillus subtilis SMC complexes are topologically loaded at centromeric sites adjacent to the replication origin by the partitioning protein ParB. These ring-shaped ATPases then translocate down the left and right chromosome arms while tethering them together. Here we show that the site-specific recombinase XerD that resolves chromosome dimers is required to unload SMC tethers when they reach the terminus. We identify XerD-specific binding sites in the terminus region and show that they dictate the site of unloading in a manner that depends on XerD but not its catalytic residue, its partner protein XerC, or the recombination site dif. Finally, we provide evidence that ParB and XerD homologs perform similar functions in Staphylococcus aureus. Thus, loading and unloading of SMC complexes are mediated by two broadly conserved factors: one involved in origin segregation, the other in terminus resolution. Similar site-specific unloading activities could modulate eukaryotic SMC complexes during interphase and mitosis.

2021-02-24 | GSE144742 | GEO

XerD is required to unload bacterial SMC complexes at the replication terminus

Project description:XerD is required to unload bacterial SMC complexes at the replication terminus

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The bacterial chromosome: architecture and action of bacterial SMC and SMC-like complexes.

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Bacillus subtilis SMC complexes juxtapose chromosome arms as they travel from origin to terminus.

Project description:Structural maintenance of chromosomes (SMC) complexes play critical roles in chromosome dynamics in virtually all organisms, but how they function remains poorly understood. In the bacterium Bacillus subtilis, SMC-condensin complexes are topologically loaded at centromeric sites adjacent to the replication origin. Here we provide evidence that these ring-shaped assemblies tether the left and right chromosome arms together while traveling from the origin to the terminus (>2 megabases) at rates >50 kilobases per minute. Condensin movement scales linearly with time, providing evidence for an active transport mechanism. These data support a model in which SMC complexes function by processively enlarging DNA loops. Loop formation followed by processive enlargement provides a mechanism by which condensin complexes compact and resolve sister chromatids in mitosis and by which cohesin generates topologically associating domains during interphase.

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Bacillus subtilis SMC complexes juxtapose chromosome arms as they travel from origin to terminus

Project description:Structural maintenance of chromosomes (SMC) complexes play critical roles in chromosome dynamics in virtually all organisms but how they function remains poorly understood. In Bacillus subtilis, SMC condensin complexes are topologically loaded at centromeric sites adjacent to the replication origin. Here we provide evidence that these ring-shaped assemblies tether the left and right chromosome arms together while traveling from the origin to the terminus (>2 Mb) at rates >50kb/min. Condensin movement scales linearly with time arguing for an active transport mechanism. These data support a model in which SMC complexes function by processively enlarging DNA loops. Loop formation followed by processive enlargement provides a mechanism for how condensin complexes compact and resolve sister chromatids in mitosis and how cohesin generates topologically associating domains (TADs) during interphase.

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Architecture of bacterial replication initiation complexes: orisomes from four unrelated bacteria.

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Evidence for binary Smc complexes lacking kite subunits in archaea.

Project description:SMC complexes play a central role in chromosome organization in all domains of life. The bacterial Smc-ScpAB complex is a three-subunit complex composed of Smc, ScpA and ScpB. ScpA bridges the two ATPase domains of the Smc homodimer, while ScpB, which belongs to the kite family of proteins, interacts with ScpA. The three subunits are known to be equally important for the function of Smc-ScpAB in bacteria. From crystallographic and biochemical studies, evidence is provided that six archaeal ScpA proteins are unable to interact with the only putative ScpB found in these species. Structure-based sequence alignment reveals that these archaeal ScpAs lack the ScpB-binding segment that is commonly present in the middle of bacterial ScpA sequences, which is thus responsible for their inability to interact with ScpB. ScpA proteins lacking the ScpB-binding segment are found to prevail in archaea. Moreover, two archaeal ScpA proteins with a longer middle region also failed to bind their putative ScpB partner. Furthermore, all or most species belonging to five out of 14 euryarchaeotal orders contain Smc and ScpA but not a detectable ScpB homologue. These data support the notion that archaeal Smc-based complexes generally function as a two-subunit complex composed of only Smc and ScpA.

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SMC complexes differentially compact mitotic chromosomes according to genomic context.

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Bacterial chromosome organization by collective dynamics of SMC condensins.

Project description:A prominent organizational feature of bacterial chromosomes was revealed by Hi-C experiments, indicating anomalously high contacts between the left and right chromosomal arms. These long-range contacts have been attributed to various nucleoid-associated proteins, including the ATPase Structural Maintenance of Chromosomes (SMC) condensin. Although the molecular structure of these ATPases has been mapped in detail, it still remains unclear by which physical mechanisms they collectively generate long-range chromosomal contacts. Here, we develop a computational model that captures the subtle interplay between molecular-scale activity of slip-links and large-scale chromosome organization. We first consider a scenario in which the ATPase activity of slip-links regulates their DNA-recruitment near the origin of replication, while the slip-link dynamics is assumed to be diffusive. We find that such diffusive slip-links can collectively organize the entire chromosome into a state with aligned arms, but not within physiological constraints. However, slip-links that include motor activity are far more effective at organizing the entire chromosome over all length-scales. The persistence of motor slip-links at physiological densities can generate large, nested loops and drive them into the bulk of the DNA. Finally, our model with motor slip-links can quantitatively account for the rapid arm-arm alignment of chromosomal arms observed in vivo.

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