Compartmentalisation via liquid-liquid phase separation in cells (360G-Wellcome-202320_Z_16_Z)

Cells spatially and temporally isolate molecules in subcellular compartments to both facilitate and regulate their interactions. In addition to organelles formed by membrane-encapsulation, cells possess membraneless organelles such as nucleoli, Cajal bodies, stress-granules and nuage. These bodies are highly dynamic, and rapidly assemble and dissolve following changes in the cellular environment and cell cycle. They are predominantly associated with nucleic acid biochemistry, and have been linked with neurodegenerative diseases and viral infection. Membraneless compartments typically display the properties of liquid droplets, and form by phase separation of disordered and multivalent proteins, making them exceedingly difficult to isolate and study. By reconstituting model membraneless organelles in cells and in vitro, I have taken significant steps towards characterising their properties. My research shows that their interior solvent environment is distinct from the bulk water in the cell, capable of localizing proteins and nucleic acids, and modulating their structure. However, the biochemical consequences of performing reactions in such environments are unexplored. I propose to use an interdisciplinary approach to explain how liquid-liquid phase separation provides a general organizing principle in cells, and study how the internal organelle environment influences biochemical reactions performed by helicase, nuclease and polymerase enzymes.