Cover: The ability of an RNA aptamer to mimic the DNA double helix is illustrated in this structural comparison. Depicted are idealized B-form DNA (left, red), the solution NMR structure of a 29-nucleotide anti-NF-κB RNA aptamer (center, blue), and idealized A-form RNA (right, brown). A combination of unpaired and stacked bases in the aptamer internal loop endows the folded RNA with helicoidal parameters and major groove geometry similar to DNA, allowing recognition by a DNA-binding transcription factor. For further details, see the article by Reiter et al. (Nucleic Acids Res. 2008;36:1227–1236).
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