Compaction of RNA Duplexes in the Cell*

Area of Science:

• Biophysics
• Molecular Biology
• Structural Biology

Background:

• The cellular microenvironment significantly influences the structure and dynamics of nucleic acids like RNA.
• Understanding how RNA structure adapts to intracellular conditions is crucial for comprehending its biological functions.

Purpose of the Study:

• To investigate the structural changes of double-stranded RNA (dsRNA) upon internalization into Xenopus laevis oocytes.
• To identify the factors contributing to dsRNA structural modifications within a cellular environment.

Main Methods:

• Utilized pulsed electron-electron double-resonance (PELDOR/DEER) spectroscopy with advanced labeling techniques.
• Employed atomic-resolution molecular dynamics simulations.
• Reconstituted dsRNA compaction in a crowded protein solution model.

Main Results:

• Observed that dsRNA adopts a more compact A-helical structure within Xenopus laevis oocytes compared to dilute solutions.
• Successfully recapitulated this compaction effect using a crowded protein solution.
• Molecular dynamics simulations supported the experimental findings, identifying electrostatic interactions as a key driver.

Conclusions:

• The intracellular environment induces significant compaction of dsRNA.
• Non-specific electrostatic interactions between proteins and dsRNA are a primary mechanism for this observed compaction.
• These findings provide insights into the structural regulation of RNA within cells.