Repulsive electrostatic interactions modulate dense and dilute phase properties of biomolecular condensates

Abstract

Liquid-like membraneless organelles form via multiple, weak interactions between biomolecules. The resulting condensed states constitute novel solvent environments inside eukaryotic cells that partition biomolecules and may favour particular biochemical reactions. Here we demonstrate that, in addition to attractive interactions, repulsive electrostatic interactions modulate condensate properties. We find that net charge modulates the formation, morphology and solvent properties of model Ddx4 condensates in cells and in vitro and that a net negative charge is conserved across germ cell-specific Ddx4 orthologues. This conserved net charge provides a sensitivity to multivalent cations that is not observed in somatic paralogues. The disfavouring effect of a net negative charge in Ddx4 orthologues appears to be offset by increased charge patterning, indicating that fine tuning of both attractive and repulsive interactions can create responsive solvent environments inside biomolecular condensates.

Deciphering how naturally occurring sequence features impact the phase behaviors of disordered prion-like domains

“…Phase separation of A1-LCD variants is destabilized as NCPR increases either in the positive or negative direction. These results are congruent with recent reports for a very different low complexity domain from DDX4 33 . Interestingly, the optimum NCPR that maximizes the driving forces for phase separation of A1-LCD and designed variants thereof is ≈+0.02.…”

“…1f). These analyses were motivated by results that highlight the role of Arg as a sticker 16 , the relative weakness of Lys as a sticker 16, 22, 23, 31, 32 , the contributions of charged residues that destabilize phase separation either as spacers that promote solvation 27, 28 or via electrostatic repulsions 33 , and the suggestion that Tyr is likely to be a stronger sticker than Phe 16, 34 .…”

Disease‐linked TDP‐43 hyperphosphorylation suppresses TDP‐43 condensation and aggregation

“…It seems possible that the number of phosphorylation sites, but not their exact position, is critical for the suppression of TDP‐43 condensation, which would indicate that multisite phosphorylation may regulate TDP‐43 phase separation through bulk electrostatics, as previously shown for other proteins (Serber & Ferrell, 2007 ; Strickfaden et al , 2007 ). Indeed, two recent studies showed that the net charge of IDR‐containing RBPs tunes their driving force for assembly (preprint: Crabtree et al , 2020 ; preprint: Bremer et al , 2021 ). For instance, reducing the net charge of the disordered region of Ddx4 promotes its phase separation (preprint: Crabtree et al , 2020 ), and increasing the net charge of the low complexity region of hnRNP‐A1 reduces its phase separation, likely due to repulsive electrostatic long‐range interactions (preprint: Bremer et al , 2021 ).…”

Transcription Regulators and Membraneless Organelles Challenges to Investigate Them

“…Irrespective of the bio-macromolecules themselves, different types of interactions can affect LLPS and MLOs formation. The importance of electrostatic interactions in LLPS have been reported from a number of studies [ 25 , 26 ]. They are classified as long-range interactions and occur between oppositely charged residues.…”