Davidson Iain F, Barth Roman, Nagasaka Kota, Tang Wen, Wutz Gordana, Horn Sabrina, Janissen Richard, Stocsits Roman R, Chlosta Emilia, Bauer Benedikt W, Dekker Cees, Peters Jan-Michael
Research Institute of Molecular Pathology, Vienna BioCenter, Vienna, Austria.
Department of Bionanoscience, Kavli Institute of Nanoscience Delft, Delft University of Technology, Delft, the Netherlands.
Cell Rep. 2025 Jun 24;44(6):115856. doi: 10.1016/j.celrep.2025.115856. Epub 2025 Jun 13.
Cohesin extrudes genomic DNA into loops that promote chromatin assembly, gene regulation, and gene recombination. Loop extrusion depends on large-scale conformational changes in cohesin, but how these translocate DNA is poorly understood. Here, we provide evidence that cohesin negatively supercoils DNA during loop extrusion. Supercoiling requires the engagement of cohesin's ATPase heads, DNA clamping by these heads, and a DNA-binding site on cohesin's hinge, indicating that cohesin twists DNA when constraining it between the hinge and the clamp. A cohesin mutant defective in negative supercoiling forms shorter loops in cells, and a similar, although weaker, phenotype is observed after the depletion of topoisomerase I. These results suggest that supercoiling is an integral part of the loop-extrusion mechanism and that relaxation of supercoiled DNA is required for cohesin-mediated loop extrusion and genome architecture.
黏连蛋白将基因组DNA挤压成环，促进染色质组装、基因调控和基因重组。环挤压依赖于黏连蛋白的大规模构象变化，但这些变化如何转运DNA却知之甚少。在这里，我们提供证据表明，黏连蛋白在环挤压过程中使DNA产生负超螺旋。超螺旋需要黏连蛋白的ATP酶头部参与、这些头部对DNA的钳位以及黏连蛋白铰链上的一个DNA结合位点，这表明黏连蛋白在将DNA限制在铰链和钳位之间时会扭转DNA。一个在负超螺旋方面有缺陷的黏连蛋白突变体在细胞中形成较短的环，并且在拓扑异构酶I耗尽后观察到类似但较弱的表型。这些结果表明，超螺旋是环挤压机制的一个组成部分，并且黏连蛋白介导的环挤压和基因组结构需要超螺旋DNA的松弛。
