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Structure of two G-quadruplexes in equilibrium in the KRAS promoter

Julien Marquevielle1, Coralie Robert1, Olivier Lagrabette1

  • 1European Institute of Chemistry and Biology (IECB), ARNA laboratory, INSERM U1212 - CNRS UMR 5320, University of Bordeaux, France.

Nucleic Acids Research
|May 21, 2020
PubMed

Insights

Researchers explored KRAS G-quadruplexes (G4) as a novel therapeutic target. They identified two stable conformations of the KRAS 32R sequence, revealing key nucleotides involved in their structural exchange.

Area of Science:

  • Molecular Biology
  • Biophysics
  • Genetics

Background:

  • KRAS is a frequently mutated oncogene, posing a significant challenge in cancer therapy.
  • Targeting KRAS directly has proven difficult, necessitating alternative strategies like targeting its gene.
  • G-quadruplexes (G4) are G-rich secondary DNA structures with roles in biological processes and are potential therapeutic targets.

Purpose of the Study:

  • To investigate the structural conformations of the KRAS 32R sequence, a G-rich region within the KRAS promoter.
  • To understand the dynamic equilibrium between different G4 structures formed by the KRAS 32R sequence.
  • To identify key nucleotides and structural motifs involved in G4 formation and stability within the KRAS gene.

Main Methods:

  • Biophysical techniques were employed to study the KRAS 32R sequence.
  • Structural analysis focused on identifying the major stable conformers of the G4 structure.
  • Equilibrium dynamics between conformations were investigated using kinetic studies.

Main Results:

  • Two major stable conformations of the KRAS 32R G-quadruplex were identified.
  • A slow equilibrium (>ms) was observed between these two distinct conformations.
  • Specific nucleotides (G9, G25, G28, G32) were found to be crucial for the conformational exchange.
  • A 3' terminal triad significantly stabilized one G4 conformer, while the other remained more flexible.

Conclusions:

  • The KRAS 32R sequence can adopt distinct G4 structures with differing stability and dynamics.
  • Understanding these conformations and their interconversion is vital for developing G4-targeting therapies for KRAS-driven cancers.
  • The identified structural features provide insights for designing small molecules to selectively target specific KRAS G4 conformations.

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