Transcriptional activity generates chromatin motion that drives nuclear blebbing

Abnormal nuclear blebbing is a hallmark of human diseases, including cancers and age-related disorders. Previous work has outlined that nuclear blebbing is due to an imbalance of nuclear strength resisting actin confinement and contraction. Independent of this balance, our recent work revealed that inhibiting RNA polymerase II (RNA Pol II) suppresses nuclear blebbing, but the mechanism remains unknown. Disruption of transcriptional activity through rapid degradation of RNA Pol II via auxin inducible degron suppresses nuclear blebbing. To more finely decrease then restore transcriptional activity, we removed culture media serum and then added it back respectively. Decreasing transcriptional activity decreases nuclear bleb formation, stability, and rupture while returning transcriptional activity increases nuclear blebbing. These modulations of transcriptional activity did not alter the nuclear spring constant or actin confinement and contraction. Instead, we find that transcriptional activity regulates chromatin domain motion measured by mean square displacement (MSD) of chromatin domains labeled via transfected Cy3-dNTPs. Increasing chromatin domain motion using an established RAD51 inhibitor B02 resulted in increased nuclear blebbing. Thus, we reveal that transcriptional activity drives nuclear blebbing through chromatin motion.