Liquid–liquid phase separation is an important mechanism by which eukaryotic cells functionally organize their intracellular content and has been related to cell malignancy and neurodegenerative diseases. These cells also undergo ATP-driven mechanical fluctuations, yet the effect of these fluctuations on the liquid–liquid phase separation remains poorly understood. Here, we employ high-resolution microscopy and atomic force microscopy of live Jurkat T cells to characterize the spectrum of their mechanical fluctuations, and to relate these fluctuations to the extent of nucleoli liquid–liquid phase separation (LLPS). We find distinct fluctuation of the cytoskeleton and of the cell diameter around 110 Hz, which depend on ATP and on myosin activity. Importantly, these fluctuations negatively correlate to nucleoli LLPS. According to a model of cell viscoelasticity, we propose that these fluctuations generate mechanical work that increases intracellular homogeneity by inhibiting LLPS. Thus, active mechanical fluctuations serve as an intracellular regulatory mechanism that could affect multiple pathophysiological conditions.

液相分离是真核细胞功能性组织细胞内内容物的重要机制，并且与细胞恶性肿瘤和神经退行性疾病有关。这些细胞也经历ATP驱动的机械波动，但是这些波动对液相分离的影响仍然知之甚少。在这里，我们采用高分辨率Jurkat T细胞显微镜和原子力显微镜来表征其机械波动的光谱，并将这些波动与核仁液液相分离（LLPS）的程度相关。我们发现细胞骨架和细胞直径的明显波动在110 Hz附近，这取决于ATP和肌球蛋白的活性。重要的是，这些波动与核仁LLPS负相关。根据细胞粘弹性的模型，我们建议这些波动产生通过抑制LLPS增加细胞内同质性的机械功。因此，主动的机械波动起着可能影响多种病理生理状况的细胞内调节机制的作用。