Adsorption of RNA to interfaces of biomolecular condensates enables wetting transitions

Biomolecular condensates form via spontaneous and driven phase transitions of multivalent proteins and nucleic acids. These macromolecules can be organized in spatially inhomogeneous ways that lead to multiple coexisting dense phases with distinct macromolecular interfaces. While considerable attention has focused on the physical driving forces that give rise to phase separation from bulk solutions, the interactions that underlie adsorption driven wetting transitions remain unclear. Here, we report that pyrimidine-rich RNAs function as adsorbents that enable cascades of wetting transitions that include partial and complete wetting of condensates formed by purine-rich RNAs. Computations show that macromolecules that are scaffolds of condensates are oriented perpendicular to condensate interfaces whereas adsorbents are oriented parallel to interfaces. Our results yield heuristics for the design of synthetic materials that can be based on RNA-rich condensates featuring bespoke interfaces and distinct local microenvironments created by the interplay between scaffolds versus adsorbents.