Skip to content
PaperFren

Phase transitions

Does RNA length change how protein droplets form and hold together?

Sanchez-Burgos I, Herriott L, Collepardo-Guevara R, et al. · Biophysical journal · 2023

Open access · cc by · source: Europe PMC

Long RNAs sit in the core of protein-RNA droplets and make them more stable, while short RNAs gather at the surface and act like soap that lowers surface tension.

Save to libraryView originalAsk PaperFrenStudy view

Study at a glance

Design
Computational / modelling — Multiscale molecular dynamics: residue-resolution Mpipi simulations of FUS or PR25 with polyU RNA of 20-400 nucleotides, plus a minimal patchy-colloid plus polymer model
N
No sample size; simulations used tens to hundreds of protein copies per box (48 FUS copies in the FUS runs) across RNA lengths and RNA/protein ratios.
Population
Simulated RNA-protein condensates (FUS, PR25 peptide, polyU RNA) and patchy colloids with self-avoiding polymers
Outcome
Critical temperature (condensate stability), density profiles across condensates, interfacial free energy

Structured fields used in claim comparison tables when every cited study has a complete layer.

Key findings

Longer RNA raised droplet stability: for PR25 at the charge-neutral ratio the critical temperature rose by about 20% going from 20 to 400 nucleotides, while FUS gained only about 3%. Both systems showed reentrant behaviour, stabilising at moderate RNA and dissolving at high RNA, but longer RNA let droplets absorb more RNA before dissolving. In mixed-length droplets, long RNA concentrated in the core and short RNA at the surface, and an RNA-coated surface had roughly half the interfacial free energy of a protein-coated one. The patchy model reproduced the trends, with a 50% versus 8% boost for RNA-dependent versus self-condensing particles.

Methodology

The authors simulated droplets formed by liquid-liquid phase separation of two RNA-binding proteins, FUS (which can condense alone) and the peptide PR25 (which needs RNA), mixed with single-stranded polyU RNA of five lengths from 20 to 400 nucleotides. Keeping total RNA fixed, they varied chain length and RNA-to-protein ratio and estimated each droplet's critical temperature, its internal density profile and its interfacial free energy. They repeated the key tests with a much simpler model of sticky patchy colloids and flexible polymers.

Limitations

All results are from coarse-grained simulations with implicit water and a mean-field treatment of salt that ignores ion identity, ion condensation and divalent ions such as magnesium. Only uniform polyU RNA was modelled, not real sequences with secondary structure. Critical temperatures from the constant-pressure runs are bracketed intervals rather than exact values, and interfacial energy could not be computed for FUS droplets because they were too large to converge.

How this study connects

Role on claims

Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.

Not yet placed on a claim. This paper has study layers, but no concept page yet cites it as support, challenge, or qualifier.

Related papers in this topic

Same topic cluster — not a recommendation engine.