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A model for the solution structure of a branched, three-strand DNA complex
N B Leontis1, M T Hills, M Piotto
1Department of Chemistry, Bowling Green State University, Ohio 43403.
Journal of Biomolecular Structure & Dynamics
|October 1, 1993
Summary
This study reveals the DNA three-way junction (TWJ) structure with unpaired thymidines. The unique conformation shows continuous base stacking and exposed unpaired thymidines in the presence of Mg2+.
Area of Science:
- Molecular Biology
- Structural Biology
- Biophysics
Background:
- DNA three-way junctions (TWJs) are crucial structural motifs in nucleic acids.
- Unpaired nucleotides within TWJs contribute to complex single-stranded nucleic acid structures.
- Understanding TWJ conformation is key to deciphering nucleic acid function.
Purpose of the Study:
- To elucidate the solution structure of a DNA three-way junction (TWJ) with two unpaired thymidines.
- To investigate the conformational changes induced by Mg2+ in TWJs.
- To characterize the base stacking and nucleotide exposure within the TWJ.
Main Methods:
- Two- and three-dimensional 1H nuclear magnetic resonance (NMR) spectroscopy were employed.
- Solution structure determination of the DNA TWJ complex.
- Analysis of base pairing and stacking interactions.
Main Results:
- A unique TWJ conformation was determined in the presence of Mg2+.
- Continuous base stacking across the junction was observed for one oligonucleotide strand.
- Unpaired thymidine bases (S3-T6 and S3-T7) were found to be solvent-exposed.
- The sugar of S3-G8 was largely buried, with specific stacking interactions identified.
Conclusions:
- The study provides detailed insights into the structure of DNA TWJs with unpaired nucleotides.
- The determined conformation highlights the role of Mg2+ in stabilizing specific nucleic acid structures.
- Findings contribute to understanding the structural diversity and functional implications of non-canonical DNA structures.