Rapid Screen of Potential i-Motif Forming Sequences in DNA Repair Gene Promoters

We have studied the in vitro stability of 25 potential i-motif-forming DNA sequences found within the promoter regions of 18 different human DNA repair genes. Three widely available methods of characterization were used to rapidly assess i-motif folding and stability and comprise a simple screen for preliminary identification of physiologically relevant i-motif forming sequences. Four highly pH-stable candidate sequences were identified exhibiting pH transitions (pH at which 50% of the oligodeoxynucleotides in solution are folded) at or above pH 6.6, thermal melting temperatures above 37 degrees C and isothermal UV difference spectra characteristic of 2'-deoxycytidine imino-nitrogen protonation. These newly identified i-motif forming sequences could represent novel targets for understanding and modulating human DNA repair gene expression.