G-DNA: a twice-folded DNA structure adopted by single-stranded oligo(dG) and its implications for telomeres.
Abstract
Our dimethyl sulfate modification experiments suggest that (dG)n stretches within single-stranded DNA fragments, which represent the simplest model for telomeric sequences, adopt a complex intrastrand structure other than a simple hairpin. We present a molecular model for the DNA structure that conforms to dimethyl sulfate methylation data. The principal element of this G-DNA structure is a quadruple helix formed by pairwise antiparallel segments of the twice-folded (dG)n stretch. This quadruple core has two wide and two narrow grooves connected by three loop-shaped segments. The strong stacking interactions of the neighboring guanine tetrads and the large number of hydrogen bonds formed can be the primary reasons that such structures are favored over a common hairpin for long (dG)n stretches. Such compact structures may be formed from (dG)n stretches of telomeric sequences.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- February 1990
- DOI:
- 10.1073/pnas.87.3.867
- Bibcode:
- 1990PNAS...87..867P