Condensin controls mitotic chromosome stiffness and stability without forming a structurally contiguous scaffold
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During cell division, chromosomes must be folded into their compact mitotic form to ensure their segregation. This process is thought to be largely controlled by the action of condensin SMC protein complexes on chromatin fibers. However, how condensins organize metaphase chromosomes is not understood. We have combined micromanipulation of single human mitotic chromosomes, sub-nanonewton force measurement, siRNA interference of condensin subunit expression, and fluorescence microscopy, to analyze the role of condensin in large-scale chromosome organization. Condensin depletion leads to a dramatic (~ 10-fold) reduction in chromosome elastic stiffness relative to the native, non-depleted case. We also find that prolonged metaphase stalling of cells leads to overloading of chromosomes with condensin, with abnormally high chromosome stiffness. These results demonstrate that condensin is a main element controlling the stiffness of mitotic chromosomes. Isolated, slightly stretched chromosomes display a discontinuous condensing staining pattern, suggesting that condensins organize mitotic chromosomes by forming isolated compaction centers that do not form a continuous scaffold.
Keywordsmetaphase chromosome chromosome compaction condensin colchicine cell division mitosis structural maintenance of chromosome protein chromosome mechanics mechanobiology chromosome stretching non-histone proteins
(human) Chromosome-associated protein
Structural maintenance of chromosomes (complex)
Small interfering RNA
Nuclear envelope breakdown
Calcinosis, Raynaud’s phenomenon, Esophageal dysmotility, Sclerodactyly, and Telangiectasia (syndrome)
Dulbecco modified eagle medium
Fetal bovine serum
Pascals (SI unit of pressure)
Newton (SI unit of force)
Author contribution statement
MS, RB, JH, and JFM conceived and designed the research. MS, RB, and JH conducted experiments. MS, RB, JH, and JFM analyzed data. MS, RB, JH, and JFM wrote, read, and approved the manuscript.
This work was supported by the NIH through grants R01-GM105847, U54-CA193419 (CR-PS-OC) and a subcontract to grant U54-DK107980, and by the NSF through grants MCB-1022117, DMR-1611076, and DMR-1206868.
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