Competing Protein-RNA Interaction Networks Control Multiphase Intracellular Organization

Area of Science:

• Biophysics
• Cell Biology
• Molecular Biology

Background:

• Membraneless condensates form via liquid-liquid phase separation (LLPS).
• The biophysical rules governing condensate assembly, substructure, and coexistence are not fully understood.
• Cytoplasmic stress granules (SGs) and P-bodies are key examples of such condensates.

Purpose of the Study:

• To elucidate the biophysical mechanism of multiphase organization in cellular condensates.
• To investigate the factors controlling the composition and miscibility of SGs and P-bodies.
• To develop a general framework for understanding tunable condensate formation.

Main Methods:

• Quantitative reconstitution of SGs and P-bodies in human cells.
• Analysis of protein-interaction networks and RNA-binding domains (RBDs).
• Application of patchy colloid theory principles.

Main Results:

• Protein network competition for connecting nodes, not RNA-binding specificity or disordered segments, dictates SG and P-body composition and miscibility.
• Competitive binding of unconnected proteins prevents LLPS.
• A framework based on competing networks explains tunable condensate formation.

Conclusions:

• Multiphase condensate organization is governed by stoichiometry-dependent competition between protein networks.
• This competition provides a tunable mechanism for generating compositionally specific condensates.
• The proposed framework offers insights into the principles underlying cellular compartmentalization.