Deciphering and Engineering Reentrant Phase Transition of Intrinsically Disordered Proteins

Formation of intracellular RNA- and protein-rich granules (RNP granules) are primarily driven by liquid phase condensation of Intrinsically Disordered Proteins (IDPs). What are the molecular driving forces that control the material properties and morphology of RNP granules? Using mixtures of multivalent charged IDPs and RNA that display reentrant phase behavior, we show that (a) the condensed phase is predominantly droplet-like under equilibrium conditions, and (b) the material properties are primarily tuned by the charge regulated electrostatic interactions. Unexpectedly, hollow condensates are formed under non-equilibrium conditions by RNA influx into RNP droplets¹. We propose that this spontaneous morphological transformation of RNP droplets is actuated by RNA-mediated mixing phase transition at the droplet center. By controlling the RNA inflow using simple microfluidic designs, complex patterns of hollow condensates can be generated stochastically. Our results suggest that cellular processes that can drive an active RNA influx into RNP droplets, such as transcription, can spatiotemporally control their material properties and morphology.

1. Banerjee, P. R., et al. 2017. Angew Chem Int Ed Engl. 56(38):11354.