Multivalent Proteins Rapidly and Reversibly Phase-Separate upon Osmotic Cell Volume Change

Mol Cell. 2020 Sep 17;79(6):978-990.e5. doi: 10.1016/j.molcel.2020.08.004. Epub 2020 Aug 27.


Processing bodies (PBs) and stress granules (SGs) are prominent examples of subcellular, membraneless compartments that are observed under physiological and stress conditions, respectively. We observe that the trimeric PB protein DCP1A rapidly (within ∼10 s) phase-separates in mammalian cells during hyperosmotic stress and dissolves upon isosmotic rescue (over ∼100 s) with minimal effect on cell viability even after multiple cycles of osmotic perturbation. Strikingly, this rapid intracellular hyperosmotic phase separation (HOPS) correlates with the degree of cell volume compression, distinct from SG assembly, and is exhibited broadly by homo-multimeric (valency ≥ 2) proteins across several cell types. Notably, HOPS sequesters pre-mRNA cleavage factor components from actively transcribing genomic loci, providing a mechanism for hyperosmolarity-induced global impairment of transcription termination. Our data suggest that the multimeric proteome rapidly responds to changes in hydration and molecular crowding, revealing an unexpected mode of globally programmed phase separation and sequestration.

Keywords: cell volume; hydration; hyperosmotic stress; molecular crowding; phase separation; processing bodies; protein multivalency; self-interaction; stress granules; stress response.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cell Size
  • Cell Survival / genetics
  • Endoribonucleases / genetics*
  • Humans
  • Osmotic Pressure / physiology
  • Proteome / genetics
  • RNA Precursors / genetics*
  • Stress, Physiological / genetics*
  • Trans-Activators / genetics*
  • Transcription Termination, Genetic*


  • Proteome
  • RNA Precursors
  • Trans-Activators
  • Endoribonucleases
  • DCP1A protein, human