Dilute phase oligomerization can oppose phase separation and modulate material properties of a ribonucleoprotein condensate.

Ian Seim, Ammon E Posey, Wilton T Snead, Benjamin M Stormo, Daphne Klotsa, Rohit V Pappu, Amy S Gladfelter

Proceedings of the National Academy of Sciences of the United States of America 2022 Mar 29

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SignificanceA large subclass of biomolecular condensates are linked to RNA regulation and are known as ribonucleoprotein (RNP) bodies. While extensive work has identified driving forces for biomolecular condensate formation, relatively little is known about forces that oppose assembly. Here, using a fungal RNP protein, Whi3, we show that a portion of its intrinsically disordered, glutamine-rich region modulates phase separation by forming transient alpha helical structures that promote the assembly of dilute phase oligomers. These oligomers detour Whi3 proteins from condensates, thereby impacting the driving forces for phase separation, the protein-to-RNA ratio in condensates, and the material properties of condensates. Our findings show how nanoscale conformational and oligomerization equilibria can influence mesoscale phase equilibria.

Citation

Ian Seim, Ammon E Posey, Wilton T Snead, Benjamin M Stormo, Daphne Klotsa, Rohit V Pappu, Amy S Gladfelter. Dilute phase oligomerization can oppose phase separation and modulate material properties of a ribonucleoprotein condensate. Proceedings of the National Academy of Sciences of the United States of America. 2022 Mar 29;119(13):e2120799119