Focus on phase separation

Phase separation is an important mechanism for biomolecule condensate assembly and is involved in multiple biological activities. Understanding its molecular mechanism provides a unique perspective for gaining insights into its role in cellular physiology and for developing new tools for the manipulation of cellular function.

This Perspective discussed selective partitioning behaviors of biomolecules and small molecules and proposed that understanding the chemical properties that control their interactions within the condensates would promote drug development.

This perspective proposes general strategies for phase-separation-related biological studies, including proper experimental designs to validate and characterize phase-separation phenomena, connections to biological functions and some caveats to avoid common misunderstandings.

This Review introduces molecular features of the phase-separating biomolecules and how they affect phase-separation behavior in a complex intracellular environment, highlighting a complex interplay between structure, sequence and environment in the phase-separation process.

Protein condensates are subcellular structures that enrich and confine molecules in cells. This Review details how condensates can be engineered with responsiveness and on-demand functions, thus pushing cellular and metabolic engineering to a new level.

Prostate tumors, resistant to current antiandrogen therapies, represent a serious clinical challenge. A new report identifies androgen-receptor-dependent liquid condensates as being responsible in part for therapeutic resistance, but, encouragingly, also reveals a novel vulnerability amenable to drug targeting.

Clustering and multimerization of cell surface proteins (CSPs) are essential for triggering downstream intracellular signaling events. Membrane-anchored liquid–liquid phase-separation systems have now been developed to manipulate the spatiotemporal distribution and activation of CSPs.

Liquid–liquid phase separation can increase the rate of enzyme activity by concentrating reactants together. A phase-separating SUMOylation cascade offers conceptual and quantitative insight into the mechanisms underlying the activity enhancement.

Biomolecular condensates form and dissolve in response to a wide range of signals. A new study reports a solubility-based phosphoproteome-profiling approach, which uncovers the extensive role of phosphorylation in regulating protein partitioning into condensates across the human proteome.

The molecular mechanism through which chromatin-bound RNA-binding proteins (chrRBPs) control transcription remains obscure. A new study reveals that chrRBPs can compartmentalize RNA and transcription machinery into a phase-separated condensate, thus modulating gene expression.

Using an interdisciplinary approach, hydrogen-peroxide-induced phase separation in the intrinsically disordered regions of the TERMINATING FLOWER transcription factor proteins was shown to regulate the shoot apical meristem through repression of the floral identity gene called ANANTHA.

Phase separation of androgen receptor underlies mutation-mediated antiandrogen resistance. A phenotypic screen enabled the discovery of ET516, which disrupts androgen receptor phase separation and effectively suppresses the growth of prostate cancer.

A membrane-tethering liquid–liquid phase-separation system was developed for programmable compartmentalization of cell-surface proteins and regulation of downstream cellular activities.

SEUSS is a transcriptional adaptor that undergoes condensation after hyperosmotic stress-induced increase of molecular crowding. The SEUSS condensates are indispensable for stress tolerance via facilitating the expression of stress-related genes.

A chemically induced dimerization strategy was used to recruit SUMOylation enzymes into condensates, enabling quantification of the effect of phase separation on the activity of a SUMOylation enzyme cascade reaction.

A combination of solubility proteome profiling with phosphoproteomics enables systematic analysis of the phosphorylation status of proteins in soluble and condensate-bound pools.

Alterations in the interactions driving phase separation of the mRNA decapping complex led to conformational rearrangements in its active site, providing a mechanism to control whether substrate mRNA is stored or decapped in condensates.

An agarose hydrogel mimicking cytoskeleton stabilizes protein liquid droplets and enables precise quantification of protein percentage in phase-separated droplets and in the dispersed phases as well as intramolecular distances via NMR and EPR.

With the example of the paraspeckle protein PSPC1, Shao et al. demonstrated the synergistic interplay of promoter-associated RNA and its binding proteins in promoting transcription condensate formation and Pol II engagement and activity via phase separation.

Plants utilize naturally produced ROS in shoot apical stem cells as a developmental signal to trigger phase separation of TMF. The resulting transcriptional condensates repress expression of the floral identity gene to precisely time flowering.