TY - JOUR TI - A low Smc flux avoids collisions and facilitates chromosome organization in Bacillus subtilis AU - Anchimiuk, Anna AU - Lioy, Virginia S AU - Bock, Florian Patrick AU - Minnen, Anita AU - Boccard, Frederic AU - Gruber, Stephan A2 - Laub, Michael T A2 - Tyler, Jessica K VL - 10 PY - 2021 DA - 2021/08/04 SP - e65467 C1 - eLife 2021;10:e65467 DO - 10.7554/eLife.65467 UR - https://doi.org/10.7554/eLife.65467 AB - 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. KW - SMC complexes KW - chromosome organization KW - chromosome condensation KW - DNA loop extrusion KW - chromosome segregation KW - ParABS JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -