It's Raining Liquids: RNA Tunes Viscoelasticity and Dynamics of Membraneless Organelles

Abstract

Paradigm-shifting advances have revealed that diverse membraneless organelles originate via liquid-liquid phase separation, but how their distinct structural and functional milieux are specified is not understood. Recent work elucidates that RNA governs the biophysical characteristics of liquid droplets formed by RNA-binding proteins with low-complexity domains and can decelerate pathogenic fibrillogenesis.

Figure 1. Model of RNP Granule Formation and Regulation

RNP granule proteins often contain an IDR and a RRM. RNP granules can be formed by liquid-liquid phase separation, which rapidly increases the local concentration of IDR-containing proteins. Freshly formed RNP granules behave like liquid droplets that have weak interactions between molecules. Different RNAs participating in the separated liquid phase govern the biophysical properties and localization of the granules. Over time, the separated liquid phase matures to a more solid-like phase with strong interactions between molecules. Fibrillar structures are often observed within matured liquid droplets.