Environmental perturbations that induce a stress response in cells lead to changes in the subcellular compartmentalisation of proteins and nucleic acids. This is achieved through the formation of biomolecular condensates – organelles composed mostly of RNA and protein, that lack a surrounding membrane.
While enormous efforts worldwide are leading to insights into the biophysics underlying condensate formation, the biological functions of condensates remain relatively understudied. We, and others, have recently observed that stimulation of immune cells results in the appearance of cytosolic biomolecular condensates containing the Retinoic acid-inducible gene (RIG)-like receptors, RIG-I and MDA5 – key molecules involved in detecting pathogens which have breached the cell wall. These novel condensates partially overlap with stress granules and their formation is dependent on functional RIG-I.