Wiley, FEBS Letters, 16(589), p. 2117-2123
DOI: 10.1016/j.febslet.2015.06.025
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The folding of oncogene promoters into non-canonical DNA secondary structures is considered a strategy to control gene expression. Herein, we focused on a 30 bases sequence located upstream of the transcription start site of BRAF (Braf-176) that contains 80% of guanines. We analyzed the structural behavior of the G- and C-rich strands. By the use of spectroscopic and electrophoretic techniques we confirmed that they actually fold into a predominant antiparallel G-quadruplex and into an i-motif, respectively, and that they can coexist at nearly physiological conditions. Finally, the influence of several factors (KCl, pH, PEG₂₀₀) on the conversion of the double stranded form of the oncogene promoter into the two above mentioned non-canonical structures has been explored.