Sequence-encoded and composition-dependent protein-RNA interactions control multiphasic condensate morphologies

Multivalent protein-protein and protein-RNA interactions are the drivers of biological phase separation. Biomolecular condensates typically contain a dense network of multiple proteins and RNAs, and their competing molecular interactions play key roles in regulating the condensate composition and structure. Employing a ternary system comprising of a prion-like polypeptide (PLP), arginine-rich polypeptide (RRP), and RNA, we show that competition between the PLP and RNA for a single shared partner, the RRP, leads to RNA-induced demixing of PLP-RRP condensates into stable coexisting phases-homotypic PLP condensates and heterotypic RRP-RNA condensates. The morphology of these biphasic condensates (non-engulfing/ partial engulfing/ complete engulfing) is determined by the RNA-to-RRP stoichiometry and the hierarchy of intermolecular interactions, providing a glimpse of the broad range of multiphasic patterns that are accessible to these condensates. Our findings provide a minimal set of physical rules that govern the composition and spatial organization of multicomponent and multiphasic biomolecular condensates. Liquid ribonucleoprotein condensates typically involve a dense network of multiple proteins and RNAs. Here, the authors employ a minimal system composed of Prion-like polypeptides (PLP), Arg-rich polypeptides (RRP), and RNA to form biphasic condensates with diverse morphologies tunable via mixture stoichiometry and hierarchy of intermolecular interactions.

Automated summary

The study highlights the importance of multivalent protein-protein and protein-RNA interactions in driving biological phase separation, demonstrating how competition between different molecules can lead to the demixing of condensates into stable coexisting phases. The biphasic condensates formed by a minimal system of PLP, RRP, and RNA exhibit diverse morphologies that are tunable through mixture stoichiometry and hierarchy of intermolecular interactions. The findings provide insights into the composition and spatial organization of multicomponent biomolecular condensates.