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Solution conformation of a parallel DNA triple helix with 5' and 3' triplex-duplex junctions
J L Asensio1, T Brown, A N Lane
1Division of Molecular Structure, National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK.
Structure (London, England : 1993)
|June 16, 1999
Summary
DNA triple helix structures were determined using nuclear magnetic resonance (NMR) spectroscopy. These findings inform the design of gene-regulating antigene oligonucleotides with improved stability and specificity.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- DNA can form parallel triple helices through Hoogsteen hydrogen bonds, inhibiting transcription.
- These DNA triple helices offer potential for regulating specific genes.
Purpose of the Study:
- To determine the structures of triplex-duplex junctions.
- To understand the structural basis of specificity in DNA triple helix formation.
- To aid in designing effective antigene oligonucleotides.
Main Methods:
- Solution structures of specific DNA triple helices were solved using nuclear magnetic resonance (NMR) spectroscopy.
- The study analyzed sequences like d(GAGAGACGTA)-X-(TACGTCTCTC)-X-(CTCTCT) and d(CTCTCT)-X-(TCTCTCAGTC)-X-(GACTGAGAGA).
Main Results:
- The DNA triple helix structure exhibits altered purine residue conformation and asymmetric junctions.
- Protonated cytosine residues in the third strand influence groove widths and stability.
- Triplexes with protonated cytosine (CH+) show higher thermodynamic stability than those with terminal thymidine.
Conclusions:
- Sequence-dependent structural variations and terminal distortions impact antigene oligonucleotide design.
- Incorporating positive charges in the third strand is crucial for optimal triplex formation.
- Triplex-stabilizing ligands can be designed for sequence-specific targeting based on charge and groove width.