Bending of Canonical and G/T Mismatched DNAs

Area of Science:

• Molecular Biology
• Biophysics
• Computational Chemistry

Background:

• Mismatched base pairs in DNA affect its flexibility and curvature, roles not fully understood in mismatch repair.
• MutS/DNA complexes show DNA bending and base-pair parameter changes near mismatches.

Purpose of the Study:

• To computationally investigate DNA bending in canonical and G/T mismatched DNA in the absence of MutS.
• To compare the mismatch discrimination capabilities of various DNA geometric parameters with base-pair opening.

Main Methods:

• Biased molecular dynamics simulations were used to study DNA bending.
• Five geometric parameters were employed to analyze DNA structure, including global and local geometry.
• The effect of PHE (benzene) intercalation on DNA bending energy was assessed.

Main Results:

• No geometric parameters analyzed showed better mismatch discrimination than base-pair opening.
• The 'roll' parameter demonstrated localized DNA bending similar to experimental MutS/DNA structures.
• PHE intercalation reduced the energetic cost of DNA bending but did not improve mismatch discrimination.

Conclusions:

• Base-pair opening is a more effective discriminator of DNA mismatches than bending parameters in the absence of MutS.
• Localized bending, specifically 'roll', can replicate MutS-induced DNA deformation.
• Intercalation of molecules like PHE can influence DNA bending energetics without enhancing mismatch recognition.