Multivalent Molecules as Modulators of RNA Granule Size and Composition.

Area of Science:

• Molecular Biology
• Cell Biology
• Biophysics

Background:

• RNA granules are crucial for localized translation in eukaryotic cells.
• Mechanisms governing RNA granule formation and selectivity remain largely unknown.
• Understanding these processes is key to deciphering cellular regulation.

Purpose of the Study:

• To develop a model for RNA granule assembly.
• To investigate the roles of specific RNA sequences (A2RE), hnRNP A2 proteins, and CKAP5 (TOG) in granule formation.
• To elucidate how these components interact to control granule composition and dynamics.

Main Methods:

• A hybrid modeling approach (deterministic-stochastic-statistical) was employed.
• Experimentally measured binding interactions among core molecular components were utilized.
• Modeling involved titrating component concentrations and varying affinities and RNA valency.

Main Results:

• hnRNP A2 acts as a bivalent adaptor, modulating interactions between multivalent components (CKAP5/TOG and RNA).
• Distinct concentration regimes of hnRNP A2 regulate granule formation, disruption, and RNA selectivity.
• Non-A2RE RNA molecules can be recruited via nonspecific interactions.

Conclusions:

• RNA granule assembly is tightly controlled by multivalent molecular interactions.
• hnRNP A2 concentration is a critical regulatory factor in granule dynamics and composition.
• The model provides insights into the fundamental principles of RNA granule formation and function.