RNA sequence and structure control assembly and function of RNA condensates

Area of Science:

• Biochemistry
• Molecular Biology
• RNA Biology

Background:

• Intracellular condensates form via liquid-liquid phase separation (LLPS), primarily involving proteins and RNA.
• Recent research highlights RNA's significant role in condensate formation, yet its specific contributions are understudied.
• Existing LLPS research predominantly focuses on protein biochemistry, leaving RNA's role largely unexplored.

Purpose of the Study:

• To investigate the impact of molecular crowding, metal ions, and RNA structure on protein-free RNA condensate formation.
• To explore the potential biological functions of RNA condensates, including gene expression regulation and protection from degradation.

Main Methods:

• Utilized bacterial riboswitches as a model system to study RNA-only condensates.
• Employed molecular crowding agents (e.g., polyethylene glycol 8K) and varying Mg2+ concentrations.
• Combined computational analysis with wet-bench experiments to identify key RNA structural and sequence elements.
• Performed structure-guided design to engineer novel RNA condensate functions.

Main Results:

• Demonstrated that molecular crowding promotes RNA LLPS, forming RNA droplets.
• Showed that elevated Mg2+ concentrations can induce LLPS in specific riboswitches independently of crowding.
• Identified critical RNA structural and sequence features that facilitate protein-free condensate formation.
• Successfully engineered RNA condensates with new functions, such as ligand binding.
• Confirmed that RNA condensates protect RNA components from nuclease degradation.

Conclusions:

• RNA self-assembly is a key driver of intracellular condensate formation.
• Environmental factors (crowding, metal ions) and intrinsic RNA properties significantly regulate RNA condensate formation.
• RNA condensates may play a biological role in controlling gene expression by modulating RNA stability.
• This study provides mechanistic insights into RNA-driven LLPS and its potential regulatory functions.