Molecular Drivers of RNA Phase Separation.

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• RNA molecules orchestrate cellular biomolecular condensates and membraneless compartments.
• While protein-RNA interactions are common, RNA sequences can self-assemble independently.
• The role of ions and temperature in RNA condensate formation, particularly lower-critical solution temperatures (LCST), is not fully understood.

Purpose of the Study:

• To elucidate the molecular drivers of RNA's temperature-dependent phase behavior.
• To understand the origins of RNA lower-critical solution temperatures (LCST).
• To investigate how ionic conditions and chemical modifications affect RNA self-assembly.

Main Methods:

• Atomistic molecular simulations of RNA tetranucleotides and analogs.
• Mapping thermodynamic profiles and structural ensembles across temperatures and ionic conditions.
• Analyzing base-stacking and hydrogen bonding interactions.

Main Results:

• Magnesium ions promote LCST behavior by inducing local order-disorder transitions in RNA structures.
• Demonstrated a base-specific thermal stability order: Poly(G) > Poly(A) > Poly(C) > Poly(U).
• Showed that ionic conditions and post-translational modifications can tune RNA self-assembly and condensate properties.

Conclusions:

• Molecular simulations provide insights into the origins of RNA LCST.
• RNA self-assembly is governed by base-stacking and hydrogen bonding, modulated by ions.
• Findings highlight the potential for fine-tuning RNA condensate properties through chemical and environmental modifications.