Structure of i-Motif/Duplex Junctions at Neutral pH

We report here the three-dimensional structure of an i-motif/duplex junction, determined by NMR methods at neutral pH. By including a minor groove tetrad at one side of the C:C+ stack of a monomeric i-motif, and a stem/loop hairpin at the other side, we have designed stable DNA constructs in which i-DNA and B-DNA regions coexist in a wide range of experimental conditions. This study demonstrates that i- and B-DNA are structurally compatible, giving rise to a distinctive fold with peculiar groove shapes. The effect of different residues at the i-motif/duplex interface has been explored. We also show that these constructs can be adapted to sequences of biological relevance, like that found in the promoter region of the KRAS oncogene.

Automated summary

The study demonstrates the structural compatibility of i- and B-DNA, which can coexist in stable DNA constructs. The impact of different residues at the i-motif/duplex interface is being explored, and these constructs can be adapted to sequences of biological relevance.