Protein-RNA condensation kinetics via filamentous nanoclusters

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Membraneless biomolecular condensates, driven by protein-RNA phase separation, are vital for cellular processes and disease.
• Understanding the dynamic assembly of these condensates is key to deciphering their biological roles.

Purpose of the Study:

• To elucidate the sequential events and kinetics of protein-RNA condensate formation using a viral model.
• To characterize the structural intermediates and rate-limiting steps in condensate assembly.

Main Methods:

• Experimental kinetic investigation of protein-RNA condensation.
• Cryoelectron microscopy for structural analysis.

Main Results:

• Identified a rapid initial protomer formation (protein dimer with two RNAs).
• Observed crystallization-like assembly initiated by secondary RNA binding, leading to filaments, nanoclusters (600 nm), and finally liquid coacervates.
• Primary nucleation was found to be faster than secondary nucleation and growth.

Conclusions:

• The study reveals a detailed kinetic pathway for protein-RNA condensate formation, from sub-second assembly to hydrogel-like structures.
• The findings provide insights into the fundamental mechanisms of biomolecular condensate formation relevant across life kingdoms.
• These condensates may serve as scaffolds for viral factories in infected cells.