Exploring functional transitions of the 2'-dG riboswitch aptamer

Area of Science:

• Biochemistry
• Molecular Biology
• Computational Biology

Background:

• Riboswitches are mRNA regulatory elements that change conformation to control gene expression.
• These conformational transitions occur on slow timescales, posing challenges for traditional simulation methods.

Purpose of the Study:

• To develop and validate a coarse-grained RNA structure-based model for simulating riboswitch dynamics.
• To explore the energy landscape and conformational states of the 2'-dG riboswitch aptamer domain.

Main Methods:

• Utilized a coarse-grained RNA structure-based model combining structural and electrostatic information.
• Performed molecular dynamics simulations to explore longer timescales and the riboswitch energy landscape.
• Validated simulation results against explicit solvent simulations and experimental data (SHAPE, NMR).

Main Results:

• The model accurately reproduces experimental observations and explicit solvent simulations.
• Identified a temperature range where the P1 helix is stable with ligand but flexible without.
• Revealed a multi-basin free energy profile for the aptamer, with distinct tertiary structures in ligand-free states.
• Demonstrated the stabilizing effect of Mg2+ ions on tertiary structures and the P1 helix.

Conclusions:

• The RNA structure-based model provides a simplified yet accurate approach to study slow riboswitch dynamics.
• Ligand binding and Mg2+ ions play crucial roles in stabilizing specific riboswitch conformations, particularly the P1 helix.
• The model facilitates understanding the mechanistic basis of riboswitch function and its connection to experimental observations.