| Autor: |
Pasternack, Laura B., Lin, Shwu-Bin, Chin, Tsung-Mei, Lin, Wei-Chen, Huang, Dee-Hua, Kan, Lou-Sing |
| Zdroj: |
Biophysical Journal; June 2002, Vol. 82 Issue: 6 p3170-3180, 11p |
| Abstrakt: |
In this study, we present the results of structural analysis of an 18-mer DNA 5′-T1C2T3C4T5C6C7T8C9T10C11T12A13G14A15G16A17G18-3′ by proton nuclear magnetic resonance (NMR) spectroscopy and molecular modeling. The NMR data are consistent with characteristics for triple helical structures of DNA: downfield shifting of resonance signals, typical for the H3+ resonances of Hoogsteen-paired cytosines; pH dependence of these H3+ resonance; and observed nuclear Overhauser effects consistent with Hoogsteen and Watson-Crick basepairing. A three-dimensional model for the triplex is developed based on data obtained from two-dimensional NMR studies and molecular modeling. We find that this DNA forms an intramolecular “paperclip” pyrimidine-purine-pyrimidine triple helix. The central triads resemble typical Hoogsteen and Watson-Crick basepairing. The triads at each end region can be viewed as hairpin turns stabilized by a third base. One of these turns is comprised of a hairpin turn in the Watson-Crick basepairing portion of the 18-mer with the third base coming from the Hoogsteen pairing strand. The other turn is comprised of two bases from the continuous pyrimidine portion of the 18-mer, stabilized by a hydrogen-bond from a purine. This “triad” has well defined structure as indicated by the number of nuclear Overhauser effects and is shown to play a critical role in stabilizing triplex formation of the internal triads. |
| Databáze: |
Supplemental Index |
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