演題：Bridging-induced phase separation by SMC is conserved

演者：Je-Kyung Ryu
　　（Department of Physics and Astronomy, Seoul National University, South Korea）

抄録：
Structural Maintenance of Chromosomes (SMC) protein complexes are key organizers of genome architecture through DNA loop extrusion. Cohesin establishes interphase chromatin organization, whereas condensin compacts mitotic chromosomes. While loop extrusion represents a fundamental mechanism of chromosome folding, additional processes may contribute comparably to genome organization. Here, we show that yeast cohesin, yeast condensin, human cohesin, and the archaeal SMC protein ClsN from Sulfolobus all exhibit pronounced clustering on DNA with the hallmarks of biomolecular condensation. These DNA–SMC clusters display liquid-like properties, including fusion events, rapid fluorescence recovery after photobleaching (FRAP), and dynamic exchange of SMC complexes with the surrounding environment. Strikingly, the clustering occurs in a DNA length-dependent manner: both yeast and human cohesin form clusters only on DNA molecules longer than 1–3 kilobase pairs. We propose that this phenomenon arises from bridging-induced phase separation (BIPS)—a previously unrecognized type of biological condensation—driven by multivalent DNA–protein–DNA interactions. Consistent with this model, in vivo imaging in yeast reveals that a subpopulation of cohesin associates with chromatin in a manner indicative of BIPS. Our results suggest that BIPS represents a universal property of SMC proteins. Finally, in silico simulations, we show that competition between Sulfolobus ClsN and transcription can recapitulate Hi-C chromatin compartmentalization, underscoring that biomolecular condensation by SMC proteins constitutes a fundamental and conserved principle of genome organization.

日　時：2025年12月2日（火）16：30 〜 17：00
　　     (本講演は『A Workshop for SMC freaks』(15:30-17:00)の一演題としての発表です)
場　所：吉田記念講堂