Evaluation of Cooling-Induced Liquid-Liquid Phase Separation of Ureido Polymers as a Cold-Shock Stress Granules Model

Many intracellular reactions occur in membrane-less organelles that form due to liquid-liquid phase separation (LLPS). Cold-shock stress granules, which are membrane-less organelles, are formed in response to a significant decrease in temperature and recruit biomolecules for regulation of their activities. The authors have reported that synthetic ureido copolymers exhibit cooling-induced LLPS under physiologically relevant conditions. In this study, influences of the cooling-induced LLPS of ureido polymers on enzymatic activity is investigated to evaluate whether the ureido polymers can mimic cold-shock stress granules. The enzyme β-galactosidase (β-Gal) is efficiently entrapped into phase-separated coacervates of ureido polymers upon cooling. The activity of β-Gal is significantly suppressed by the entrapment. The enzymatic activity is recovered after heating, which dissolves the coacervate. Thus, the LLPS formed by ureido polymers are a suitable model for cold-shock stress granules.