Volume 22 Issue 3, March 2021

Tatjana Trcek recounts the discovery of RNA phase separation, going back more than half a century.

Monika Fuxreiter discusses recent studies indicating that generic interactions that determine the biophysical properties of condensates are important for condensate function.

Alex Holehouse describes the contributions of Nott et al. to the understanding of the mechanisms of liquid–liquid phase separation.

mRNA translation is found to occur in cytosolic stress granules, membraneless organelles that form via liquid−liquid phase separation when cells are exposed to cell-intrinsic or environmental stress.

Changes in RNA abundance in transcriptional condensates provide dynamic feedback on transcription.

The nucleolus is a membraneless organelle involved in ribonucleoprotein assembly, including ribosome biogenesis. Recent evidence indicates that the nucleolus is a biomolecular condensate that forms via liquid–liquid phase separation (LLPS), and insights from studies within the LLPS framework are increasing our understanding of the relationship between nucleolar structure and function.

Recent studies have highlighted the contribution of RNA to cellular liquid–liquid phase separation and condensate formation. RNA features modulate the composition and biophysical properties of RNA–protein condensates, which have various cellular functions, including RNA transport and localization, supporting catalytic processes and responding to stress.

Biomolecular condensates, which form via liquid−liquid phase separation in a tightly regulated manner, have fundamental roles in cellular organization and physiology. Recent studies provide insight into how cellular stress, ageing-related loss of homeostasis and a decline in protein quality control may contribute to the formation of aberrant, disease-causing condensates.

Biomolecular condensates are membraneless molecular assemblies formed via liquid–liquid phase separation. They have a plethora of roles, ranging from controlling biochemical reactions to regulating cell organization and cell function. This article provides a framework for the study of condensate functions across these cellular length scales, offering to bring new understanding of biological processes.