Altered structural fluctuations in duplex RNA versus DNA: a conformational switch involving base pair opening

Area of Science:

• Structural Biology
• Computational Biophysics
• Nucleic Acid Chemistry

Background:

• Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) are fundamental nucleic acids with distinct structural and functional roles.
• Understanding the differential flexibility and dynamics of DNA and RNA duplexes is crucial for elucidating their biological functions.

Purpose of the Study:

• To investigate and compare the structural flexibility and dynamics of DNA and RNA duplexes using molecular dynamics (MD) simulations.
• To identify the molecular mechanisms underlying base pair opening events in RNA and their absence in DNA.

Main Methods:

• Conducting molecular dynamics (MD) simulations on a series of DNA and RNA duplexes.
• Analyzing local base pair opening events and their temporal dynamics (nanosecond timescale).
• Examining the role of solvent-base interactions, intra-strand hydrogen bonding, and nucleoside-level motion.

Main Results:

• Duplex RNA demonstrated local base pair opening events into the major groove on the nanosecond timescale, unlike DNA duplexes.
• Key factors identified for RNA base opening include solvent interactions, 2'OH(n)-O4'(n+1) intra-strand hydrogen bonding, and enhanced nucleoside rigidity.
• A 'conformational switch' involving hydrogen bonding and rigid body motion stabilizes the open base pair state in RNA.

Conclusions:

• RNA exhibits unique structural dynamics, including base pair opening, attributed to specific molecular interactions and conformational properties.
• The findings provide insights into the differential flexibility of RNA and DNA, potentially relevant to RNA's diverse biological functions.
• Observed RNA opening rates correlate with experimental data for AU base pairs and structural data from crystal structures.