Biomolecular condensates formed by liquid-liquid phase separation (LLPS) are increasingly recognized as key regulators of cellular organization and as potential precursors to pathological aggregates (implicated in neurodegenerative diseases such as Parkinson’s). Yet, the molecular steps leading to condensate formation and the internal architecture of these dynamic assemblies remains poorly understood. Our model protein, Dhh1, is an RNA helicase that represses translation and promotes mRNA decay by sequestering poorly translating mRNAs into P-bodies. With this model system, we show that RNA is not a passive scaffold but an active modulator of the physical properties of Dhh1 condensates. Optical tweezer measurements reveal that RNA length tunes the viscoelastic properties of Dhh1 condensates, suggesting a regulatory role for RNA in condensate material state. Additionally, we explore the initial stages of condensate formation using interferometric scattering (iSCAT) microscopy to detect and track nanoclusters that we hypothesize to represent nucleation intermediates. Ongoing work includes further developing label-free strategies to characterize and track these nanoclusters and its consequences on condensate internal architecture.
Pang et al. (Sun,) studied this question.