A Molecular Grammar Governing the Driving Forces for Phase Separation of Prion-like RNA Binding Proteins

Cell. 2018 Jul 26;174(3):688-699.e16. doi: 10.1016/j.cell.2018.06.006. Epub 2018 Jun 28.


Proteins such as FUS phase separate to form liquid-like condensates that can harden into less dynamic structures. However, how these properties emerge from the collective interactions of many amino acids remains largely unknown. Here, we use extensive mutagenesis to identify a sequence-encoded molecular grammar underlying the driving forces of phase separation of proteins in the FUS family and test aspects of this grammar in cells. Phase separation is primarily governed by multivalent interactions among tyrosine residues from prion-like domains and arginine residues from RNA-binding domains, which are modulated by negatively charged residues. Glycine residues enhance the fluidity, whereas glutamine and serine residues promote hardening. We develop a model to show that the measured saturation concentrations of phase separation are inversely proportional to the product of the numbers of arginine and tyrosine residues. These results suggest it is possible to predict phase-separation properties based on amino acid sequences.

Keywords: FUS; PLD; cation-π; intrinsically disordered; low complexity; membraneless compartments; phase separation; prion-like; prion-like RNA binding proteins; saturation concentration.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Amino Acids / chemistry
  • Animals
  • Arginine / chemistry
  • Computer Simulation
  • HeLa Cells
  • Humans
  • Intrinsically Disordered Proteins / genetics
  • Intrinsically Disordered Proteins / physiology
  • Phase Transition
  • Prion Proteins / chemistry
  • Prion Proteins / genetics
  • Prions / genetics
  • Prions / physiology
  • Protein Domains
  • RNA-Binding Protein FUS / genetics*
  • RNA-Binding Protein FUS / physiology
  • RNA-Binding Proteins / isolation & purification
  • RNA-Binding Proteins / physiology*
  • Sf9 Cells
  • Tyrosine / chemistry


  • Amino Acids
  • Intrinsically Disordered Proteins
  • Prion Proteins
  • Prions
  • RNA-Binding Protein FUS
  • RNA-Binding Proteins
  • Tyrosine
  • Arginine