Poster abstracts

Poster number 28 submitted by Taranpreet Kaur

RNA Regulates the Morphology of Multiphasic Biomolecular Condensates

Taranpreet Kaur (Department of Physics, University at Buffalo, Buffalo, NY, USA), Muralikrishna Raju (Department of Chemistry, Iowa State University, Ames IA, USA), Ibraheem Alshareedah (Department of Physics, University at Buffalo, Buffalo, NY, USA), Richoo B. Davis (Department of Physics, University at Buffalo, Buffalo, NY, USA), Davit A. Potoyan (Department of Chemistry, Iowa State University, Ames IA, USA), Priya R. Banerjee (Department of Physics, University at Buffalo, Buffalo, NY, USA)

Abstract:
Biomolecular condensates formed through liquid-liquid phase separation (LLPS) such as the nucleolus, para-speckles and stress granules are known to organize into multi-layered structures in vivo with distinct sub-compartments. This multilayered structuring is a result of LLPS of constituents into multiple coexisting phases driven by many-body interactions within a dense network of proteins and RNA. Utilizing a model multicomponent system comprising of a Prion-like polypeptide (PLP), an Arginine-rich polypeptide (RLP), and RNA, we investigate the role of competitive RNA-protein and protein-protein interactions in regulating the composition and spatial organization of biomolecular condensates. We show that in absence of RNA, RLP enhances the phase separation of PLP, forming associative PLP-RLP condensates. Contrastingly, in the presence of RNA, competition between PLP and RNA for the shared binding partner (RLP) leads to PLP-RLP de-mixing into bi-phasic condensates with distinct compositions. Employing a combination of biophysical experiments and computer simulation, we reveal a rich variety of multiphasic pattering of these co-existing condensates ranging from completely engulfed to partially engulfed to completely separated as well as Janus droplets. We show that these diverse patterns of bi-phasic condensates can be controlled via changing the amount of RNA as well as sequence perturbations within the RNA-protein interaction network. These results establish a hitherto unknown link between relative interfacial energies of coexisting fluids at the mesoscale and the protein-RNA interactions at the molecular level. In essence, our results shed light on the phase-behavior of a multi-component RNA-protein system and uncover a regulatory role of competitive RNA-protein interactions in dictating the spatial organization of multiphasic bio-condensates.

Keywords: Liquid-Liquid phase separation, Multi-layered bio-condensates