A low Smc flux avoids collisions and facilitates chromosome organization in Bacillus subtilis

SMC complexes are widely conserved ATP-powered DNA-loop-extrusion motors indispensable for organizing and faithfully segregating chromosomes. 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...

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Bibliographic Details
Published in:eLife 2021-08, Vol.10
Main Authors: Anchimiuk, Anna, Lioy, Virginia S, Bock, Florian Patrick, Minnen, Anita, Boccard, Frederic, Gruber, Stephan
Format: Article
Language:English
Subjects:
Amino acids
Bacteria
Biochemistry, Molecular Biology
chromosome condensation
chromosome organization
chromosome segregation
Chromosomes
Chromosomes and Gene Expression
Cloning
Deoxyribonucleic acid
DNA
DNA loop extrusion
Experiments
Genetic aspects
Genomes
Life Sciences
Microbiology and Infectious Disease
ParABS
Proteins
RNA polymerase
SMC complexes
Streptococcus infections
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Summary:SMC complexes are widely conserved ATP-powered DNA-loop-extrusion motors indispensable for organizing and faithfully segregating chromosomes. 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 residency 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 limited. Altogether, we identify mechanisms that help to avoid Smc collisions and their resolution by Smc traversal or other potentially risky molecular transactions.
ISSN:2050-084X
2050-084X
DOI:10.7554/eLife.65467