Rules of engagement for condensins and cohesins guide mitotic chromosome formation

Editor’s summary
Structural maintenance of chromosomes (SMC) protein complexes, which include cohesin and condensin, play crucial roles in chromatin organization during the interphase and mitosis steps of the cell cycle. Samejima et al. investigated how these complexes interact and guide mitotic chromosome formation. Using chromatin structure analysis, imaging, proteomics, and polymer modeling, the investigators explored the “rules of engagement” for SMC complexes as cells transitioned from interphase to mitosis. They found that condensin disassembles interphase chromatin structures by evicting or displacing cohesin while bypassing cohesive cohesin to maintain sister chromatid cohesion. This study also examined the dynamics of loop extrusion by condensins in vivo and the impact of cohesin depletion on mitotic chromosome organization. —Di Jiang DOI: 10.1126/science.adq1709