Double-stranded RNA under force and torque: similarities to and striking differences from double-stranded DNA

Area of Science:

• Biophysics
• Molecular Biology
• Genetics

Background:

• RNA's mechanical properties, particularly double-stranded RNA (dsRNA), are crucial for genetic information transmission and regulation.
• While double-stranded DNA (dsDNA) mechanics are well-understood, dsRNA mechanics remain largely uncharacterized.

Purpose of the Study:

• To comprehensively characterize the mechanical properties of dsRNA under external forces and torques.
• To compare dsRNA mechanics with those of dsDNA and identify unique behaviors.

Main Methods:

• Utilized magnetic tweezers to apply controlled forces and torques to dsRNA.
• Analyzed dsRNA conformational transitions and force-torque phase diagrams.

Main Results:

• dsRNA exhibits a force-torque phase diagram similar to dsDNA, including plectoneme formation and torque-induced helix melting.
• Identified unique dsRNA behaviors: shortening upon overwinding and significantly slower transition rates at the plectonemic buckling transition compared to dsDNA.
• Observed highly overwound (P-RNA) and left-handed (L-RNA) states in dsRNA.

Conclusions:

• dsRNA possesses distinct mechanical properties that differ from dsDNA, challenging existing nucleic acid mechanics models.
• Provides essential baseline data for modeling RNA behavior in biological systems.
• Opens avenues for single-molecule studies on RNA-protein interactions involving twist and torque.