Probing Watson-Crick and Hoogsteen base pairing in duplex DNA using dynamic nuclear polarization solid-state NMR...

Area of Science:

• Biochemistry
• Structural Biology
• Spectroscopy

Background:

• DNA typically exists in Watson-Crick base pairing geometry.
• Hoogsteen conformations are alternative base pair geometries crucial for DNA-protein and DNA-small molecule interactions.
• Detecting Hoogsteen base pairs in large DNA complexes is difficult with traditional methods.

Purpose of the Study:

• To introduce a novel spectroscopic technique for identifying and differentiating Watson-Crick and Hoogsteen DNA base pairs.
• To demonstrate the utility of multidimensional dynamic nuclear polarization-enhanced solid-state NMR for analyzing DNA structures.

Main Methods:

• Utilized multidimensional dynamic nuclear polarization-enhanced solid-state NMR spectroscopy.
• Analyzed characteristic NMR chemical shifts and internuclear dipolar couplings.
• Applied the method to a model 12-mer DNA duplex and the Widom 601 DNA nucleosome core particle.

Main Results:

• Successfully distinguished between Watson-Crick and Hoogsteen base pairs using the developed NMR approach.
• Demonstrated the method's applicability on both small DNA duplexes and large nucleosome core particles.
• Observed characteristic NMR signals indicative of Hoogsteen geometry in DNA-echinomycin complexes.

Conclusions:

• Multidimensional dynamic nuclear polarization-enhanced solid-state NMR is a powerful tool for studying DNA base pairing geometries.
• This technique overcomes limitations of traditional methods for analyzing Hoogsteen base pairs in complex DNA systems.
• The findings provide new insights into DNA structural dynamics and interactions relevant to biological function.