Tracing Effects of Fluorine Substitutions on G‑Quadruplex Conformational Changes

A human telomere sequence that folds into an intramolecular (3 + 1)-hybrid G-quadruplex was modified by the incorporation of 2′-fluoro-2′-deoxyriboguanosines (FG) into syn positions of its outer tetrad. A circular dichroism and NMR spectral analysis reveals a nearly quantitative switch of the G-tetr...

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Bibliographic Details
Published in:ACS chemical biology 2017-05, Vol.12 (5), p.1308-1315
Main Authors: Dickerhoff, Jonathan, Haase, Linn, Langel, Walter, Weisz, Klaus
Format: Article
Language:English
Subjects:
Deoxyguanosine - chemistry
Fluorine - chemistry
G-Quadruplexes
Humans
Nuclear Magnetic Resonance, Biomolecular
Nucleic Acid Conformation
Telomere - genetics
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Summary:A human telomere sequence that folds into an intramolecular (3 + 1)-hybrid G-quadruplex was modified by the incorporation of 2′-fluoro-2′-deoxyriboguanosines (FG) into syn positions of its outer tetrad. A circular dichroism and NMR spectral analysis reveals a nearly quantitative switch of the G-tetrad polarity with concerted syn↔anti transitions of all four G residues. These observations follow findings on a FG-substituted (3 + 1)-hybrid quadruplex with a different fold, suggesting a more general propensity of hybrid-type quadruplexes to undergo a tetrad polarity reversal. Two out of the three FG analogs in both modified quadruplexes adopt an S-type sugar pucker, challenging a sole contribution of N-type sugars in enforcing an anti glycosidic torsion angle associated with the tetrad flip. NMR restrained three-dimensional structures of the two substituted quadruplexes reveal a largely conserved overall fold but significant rearrangements of the overhang and loop nucleotides capping the flipped tetrad. Sugar pucker preferences of the FG analogs may be rationalized by different orientations of the fluorine atom and its resistance to be positioned within the narrow groove with its highly negative electrostatic potential and spine of water molecules.
ISSN:1554-8929
1554-8937
DOI:10.1021/acschembio.6b01096