Single-Molecule Conformational Analysis of G-Quadruplex Formation in the Promoter DNA Duplex of the Proto-Oncogene C-Kit

Herein we report on the single-molecule analysis of a conserved DNA quadruplex element found in the transcriptional activation site of the promoter of the proto- oncogene c-kit. We demonstrate that the c-kit quadruplex motif is able to fold into nonduplex states within a natural extended DNA duplex. There are apparent differences in putative quadruplex structures, and the K+ dependence on quadruplex formation, that appear to result when studying this quadruplex motif in natural duplex, as opposed to the single-stranded form.