Mechanistic Insights into the Ligand-Induced Unfolding of an RNA G-Quadruplex

J Am Chem Soc. 2022 Jan 19;144(2):935-950. doi: 10.1021/jacs.1c11248. Epub 2022 Jan 6.

Abstract

The cationic porphyrin TMPyP4 is a well-established DNA G-quadruplex (G4) binding ligand that can stabilize different topologies via multiple binding modes. However, TMPyP4 can have both a stabilizing and destabilizing effect on RNA G4 structures. The structural mechanisms that mediate RNA G4 unfolding remain unknown. Here, we report on the TMPyP4-induced RNA G4 unfolding mechanism studied by well-tempered metadynamics (WT-MetaD) with supporting biophysical experiments. The simulations predict a two-state mechanism of TMPyP4 interaction via a groove-bound and a top-face-bound conformation. The dynamics of TMPyP4 stacking on the top tetrad disrupts Hoogsteen H-bonds between guanine bases, resulting in the consecutive TMPyP4 intercalation from top-to-bottom G-tetrads. The results reveal a striking correlation between computational and experimental approaches and validate WT-MetaD simulations as a powerful tool for studying RNA G4-ligand interactions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cations / chemistry
  • G-Quadruplexes*
  • Hydrogen Bonding
  • Intercalating Agents / chemistry
  • Ligands*
  • Molecular Dynamics Simulation
  • Nucleic Acid Conformation
  • Porphyrins / chemistry*
  • Thermodynamics

Substances

  • Cations
  • Intercalating Agents
  • Ligands
  • Porphyrins
  • tetra(4-N-methylpyridyl)porphine