scholarly journals Chromosome remodelling by SMC/Condensin in B. subtilis is regulated by Soj/ParA during growth and sporulation

2021 ◽  
Author(s):  
David M Roberts ◽  
Anna Anchimiuk ◽  
Tomas G Kloosterman ◽  
Heath Murray ◽  
Ling Juan Wu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Bacillus Subtilis ◽  
Chromosome Segregation ◽  
Chromosome Structure ◽  
Replication Initiation ◽  
Chromosome Organization ◽  
Filament Formation ◽  
Axial Filament ◽  
Dna Replication Initiation ◽  
The Web

SMC complexes, loaded at ParB-parS sites, are key mediators of chromosome organization in bacteria. ParA/Soj proteins interact with ParB/Spo0J in a pathway involving ATP-dependent dimerization and DNA binding, leading to chromosome segregation and SMC loading. In Bacillus subtilis, ParA/Soj also regulates DNA replication initiation, and along with ParB/Spo0J is involved in cell cycle changes during endospore formation. The first morphological stage in sporulation is the formation of an elongated chromosome structure called an axial filament. We now show that a major redistribution of SMC complexes drives axial filament formation, in a process regulated by ParA/Soj. Unexpectedly, this regulation is dependent on monomeric forms of ParA/Soj that cannot bind DNA or hydrolyse ATP. These results reveal a new role for ParA/Soj proteins in the regulation of SMC dynamics in bacteria, and yet further complexity in the web of interactions involving chromosome replication, segregation, and organization, controlled by ParAB and SMC.

scholarly journals Regulation of DNA Replication Initiation by Chromosome Structure

2015 ◽  
Vol 197 (21) ◽  
pp. 3370-3377 ◽  
Author(s):  
David Magnan ◽  
David Bates
Keyword(s):  
Cell Cycle ◽  
Phase Transitions ◽  
Growth Phase ◽  
Chromosome Structure ◽  
Regulatory Mechanism ◽  
Replication Initiation ◽  
Dna Replication Initiation ◽  
Genetic Switches ◽  
Structure Density ◽  
Nucleoid Structure

Recent advancements in fluorescence imaging have shown that the bacterial nucleoid is surprisingly dynamic in terms of both behavior (movement and organization) and structure (density and supercoiling). Links between chromosome structure and replication initiation have been made in a number of species, and it is universally accepted that favorable chromosome structure is required for initiation in all cells. However, almost nothing is known about whether cells use changes in chromosome structure as a regulatory mechanism for initiation. Such changes could occur during natural cell cycle or growth phase transitions, or they could be manufactured through genetic switches of topoisomerase and nucleoid structure genes. In this review, we explore the relationship between chromosome structure and replication initiation and highlight recent work implicating structure as a regulatory mechanism. A three-component origin activation model is proposed in which thermal and topological structural elements are balanced withtrans-acting control elements (DnaA) to allow efficient initiation control under a variety of nutritional and environmental conditions. Selective imbalances in these components allow cells to block replication in response to cell cycle impasse, override once-per-cell-cycle programming during growth phase transitions, and promote reinitiation when replication forks fail to complete.

scholarly journals Activation of a signaling pathway by the physical translocation of a chromosome

2021 ◽  
Author(s):  
Mathilde Guzzo ◽  
Allen G. Sanderlin ◽  
Lennice K. Castro ◽  
Michael T. Laub
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Signaling Pathway ◽  
Chromosome Segregation ◽  
Caulobacter Crescentus ◽  
Replication Initiation ◽  
Dna Replication Initiation ◽  
Cellular Processes ◽  
Initiation Of Dna Replication

AbstractIn every organism, the cell cycle requires the execution of multiple cellular processes in a strictly defined order. However, the mechanisms used to ensure such order remain poorly understood, particularly in bacteria. Here, we show that the activation of the essential CtrA signaling pathway that triggers cell division in Caulobacter crescentus is intrinsically coupled to the successful initiation of DNA replication via the physical translocation of a newly-replicated chromosome, powered by the ParABS system. We demonstrate that ParA accumulation at the new cell pole during chromosome segregation recruits ChpT, an intermediate component of the CtrA signaling pathway. ChpT is normally restricted from accessing the selective PopZ polar microdomain until the new chromosome and ParA arrive. Consequently, any disruption to DNA replication initiation prevents the recruitment of ChpT and, in turn, cell division. Collectively, our findings reveal how major cell-cycle events are coordinated in Caulobacter and, importantly, how the physical translocation of a chromosome triggers an essential signaling pathway.

scholarly journals Effects of oriC relocation on control of replication initiation in Bacillus subtilis

Microbiology ◽  
2009 ◽  
Vol 155 (9) ◽  
pp. 3070-3082 ◽  
Author(s):  
Shigeki Moriya ◽  
Yoshikazu Kawai ◽  
Sakiko Kaji ◽  
Adrian Smith ◽  
Elizabeth J. Harry ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Bacillus Subtilis ◽  
Dna Replication ◽  
Negative Control ◽  
Replication Initiation ◽  
Control Mechanisms ◽  
Bacterial Cells ◽  
Wild Type ◽  
Dna Replication Initiation ◽  
In The Wild

In bacteria, DNA replication initiation is tightly regulated in order to coordinate chromosome replication with cell growth. In Escherichia coli, positive factors and negative regulatory mechanisms playing important roles in the strict control of DNA replication initiation have been reported. However, it remains unclear how bacterial cells recognize the right time for replication initiation during the cell cycle. In the Gram-positive bacterium Bacillus subtilis, much less is known about the regulation of replication initiation, specifically, regarding negative control mechanisms which ensure replication initiation only once per cell cycle. Here we report that replication initiation was greatly enhanced in strains that had the origin of replication (oriC) relocated to various loci on the chromosome. When oriC was relocated to new loci further than 250 kb counterclockwise from the native locus, replication initiation became asynchronous and earlier than in the wild-type cells. In two oriC-relocated strains (oriC at argG or pnbA, 25 ° or 30 ° on the 36 ° chromosome map, respectively), DnaA levels were higher than in the wild-type but not enough to cause earlier initiation of replication. Our results suggest that the initiation capacity of replication is accumulated well before the actual time of initiation, and its release may be suppressed by a unique DNA structure formed near the native oriC locus.

scholarly journals DNA Content and Nucleoid Distribution in Methanothermobacter thermautotrophicus

2005 ◽  
Vol 187 (5) ◽  
pp. 1856-1858 ◽  
Author(s):  
Alan I. Majerník ◽  
Magnus Lundgren ◽  
Paul McDermott ◽  
Rolf Bernander ◽  
James P. J. Chong
Keyword(s):  
Flow Cytometry ◽  
Dna Replication ◽  
Chromosome Segregation ◽  
Dna Content ◽  
Replication Initiation ◽  
Epifluorescence Microscopy ◽  
Single Chromosome ◽  
Dna Replication Initiation ◽  
Methanothermobacter Thermautotrophicus ◽  
Multiple Cells

ABSTRACT Flow cytometry and epifluorescence microscopy results for the euryarchaeon Methanothermobacter thermautotrophicus were consistent with filaments containing multiple cells. Filaments of one to four cells contained two to eight nucleoids. Single chromosome-containing cells were not observed. Filaments containing multiple genome copies displayed synchronous DNA replication initiation. Chromosome segregation occurred during replication or rapidly after replication termination.

scholarly journals Cohesion of Sister Chromosome Termini during the Early Stages of Sporulation in Bacillus subtilis

2020 ◽  
Vol 202 (20) ◽  
Author(s):  
Clare Willis ◽  
Jeff Errington ◽  
Ling Juan Wu
Keyword(s):  
Cell Cycle ◽  
Bacillus Subtilis ◽  
Mother Cell ◽  
Developmental Process ◽  
Time Lapse ◽  
Axial Filament ◽  
Content Type ◽  
Early Stages ◽  
Cell Compartments ◽  
Sister Chromosome

ABSTRACT During sporulation of Bacillus subtilis, the cell cycle is reorganized to generate separated prespore and mother cell compartments, each containing a single fully replicated chromosome. The process begins with reorganization of the nucleoid to form an elongated structure, the axial filament, in which the two chromosome origins are attached to opposite cell poles, with the remainder of the DNA stretched between these sites. When the cell then divides asymmetrically, the division septum closes around the chromosome destined for the smaller prespore, trapping the origin-proximal third of the chromosome in the prespore. A translocation pore is assembled through which a DNA transporter, SpoIIIE/FtsK, transfers the bulk of the chromosome to complete the segregation process. Although the mechanisms involved in attaching origin regions to the cell poles are quite well understood, little is known about other aspects of axial filament morphology. We have studied the behavior of the terminus region of the chromosome during sporulation using time-lapse imaging of wild-type and mutant cells. The results suggest that the elongated structure involves cohesion of the terminus regions of the sister chromosomes and that this cohesion is resolved when the termini reach the asymmetric septum or translocation pore. Possible mechanisms and roles of cohesion and resolution are discussed. IMPORTANCE Endospore formation in Firmicutes bacteria provides one of the most highly resistant life forms on earth. During the early stages of endospore formation, the cell cycle is reorganized so that exactly two fully replicated chromosomes are generated, before the cell divides asymmetrically to generate the prespore and mother cell compartments that are critical for the developmental process. Decades ago, it was discovered that just prior to asymmetrical division the two chromosomes enter an unusual elongated configuration called the axial filament. This paper provides new insights into the nature of the axial filament structure and suggests that cohesion of the normally separated sister chromosome termini plays an important role in axial filament formation.

scholarly journals Polar Remodeling and Histidine Kinase Activation, Which Is Essential for Caulobacter Cell Cycle Progression, Are Dependent on DNA Replication Initiation

2010 ◽  
Vol 192 (15) ◽  
pp. 3893-3902 ◽  
Author(s):  
Antonio A. Iniesta ◽  
Nathan J. Hillson ◽  
Lucy Shapiro
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Histidine Kinase ◽  
Cell Cycle Progression ◽  
Caulobacter Crescentus ◽  
Replication Initiation ◽  
Cycle Progression ◽  
Dna Replication Initiation ◽  
Flagellar Biosynthesis ◽  
Initiation Of Dna Replication

ABSTRACT Caulobacter crescentus initiates a single round of DNA replication during each cell cycle. Following the initiation of DNA replication, the essential CckA histidine kinase is activated by phosphorylation, which (via the ChpT phosphotransferase) enables the phosphorylation and activation of the CtrA global regulator. CtrA∼P then blocks the reinitiation of replication while regulating the transcription of a large number of cell cycle-controlled genes. It has been shown that DNA replication serves as a checkpoint for flagellar biosynthesis and cell division and that this checkpoint is mediated by the availability of active CtrA. Because CckA∼P promotes the activation of CtrA, we addressed the question of what controls the temporal activation of CckA. We found that the initiation of DNA replication is a prerequisite for remodeling the new cell pole, which includes the localization of the DivL protein kinase to that pole and, consequently, the localization, autophosphorylation, and activation of CckA at that pole. Thus, CckA activation is dependent on polar remodeling and a DNA replication initiation checkpoint that is tightly integrated with the polar phospho-signaling cascade governing cell cycle progression.

scholarly journals Novel chromosome organization pattern in actinomycetales–overlapping replication cycles combined with diploidy

2016 ◽  
Author(s):  
Kati Böhm ◽  
Fabian Meyer ◽  
Agata Rhomberg ◽  
Jörn Kalinowski ◽  
Catriona Donovan ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Chromosome Organization ◽  
Model Species ◽  
Chromosomal Organization ◽  
Dna Segregation ◽  
Rate Dependent ◽  
Dependent Cell ◽  
Underlying Mechanisms ◽  
Cell Cycle Models

AbstractBacteria regulate chromosome replication and segregation tightly with cell division to ensure faithful segregation of DNA to daughter generations. The underlying mechanisms have been addressed in several model species. It became apparent that bacteria have evolved quite different strategies to regulate DNA segregation and chromosomal organization. We have investigated here how the actinobacteriumCorynebacterium glutamicumorganizes chromosome segregation and DNA replication. Unexpectedly, we find thatC. glutamicumcells are at least diploid under all conditions tested and that these organisms have overlapping C-periods during replication with both origins initiating replication simultaneously. Based on experimentally obtained data we propose growth rate dependent cell cycle models forC. glutamicum.

scholarly journals Wapl releases Scc1-cohesin and regulates chromosome structure and segregation in mouse oocytes

2020 ◽  
Vol 219 (4) ◽  
Author(s):  
Mariana C.C. Silva ◽  
Sean Powell ◽  
Sabrina Ladstätter ◽  
Johanna Gassler ◽  
Roman Stocsits ◽  
...  
Keyword(s):  
Residence Time ◽  
Chromosome Segregation ◽  
Chromosome Structure ◽  
Somatic Cells ◽  
Cell Types ◽  
Chromosome Organization ◽  
Loop Size ◽  
Mouse Oocytes ◽  
Single Nucleus ◽  
Meiosis I

Cohesin is essential for genome folding and inheritance. In somatic cells, these functions are both mediated by Scc1-cohesin, which in mitosis is released from chromosomes by Wapl and separase. In mammalian oocytes, cohesion is mediated by Rec8-cohesin. Scc1 is expressed but neither required nor sufficient for cohesion, and its function remains unknown. Likewise, it is unknown whether Wapl regulates one or both cohesin complexes and chromosome segregation in mature oocytes. Here, we show that Wapl is required for accurate meiosis I chromosome segregation, predominantly releases Scc1-cohesin from chromosomes, and promotes production of euploid eggs. Using single-nucleus Hi-C, we found that Scc1 is essential for chromosome organization in oocytes. Increasing Scc1 residence time on chromosomes by Wapl depletion leads to vermicelli formation and intra-loop structures but, unlike in somatic cells, does not increase loop size. We conclude that distinct cohesin complexes generate loops and cohesion in oocytes and propose that the same principle applies to all cell types and species.

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