Figure 1.

The G-rich motif associated with a meiosis-specific DSB on chromosome IV of S. cerevisiae folds into a G-quadruplex structure. (A) Given here are nucleotide sequences of G-rich WT, G-MT, and poly (dT). The guanine residues are highlighted in red. The G to T substitution in the mutant strand is denoted by green. (B) Given here is the EMSA analysis of the G-quadruplex structures formed by increasing concentrations of a ³²P-labeled G-rich WT, G-mutant and poly(dT) ODNs in the presence of 120 mM KCl. The solid triangle on top of the gel image denotes increasing concentrations of the indicated ODN. Lanes 1–4 contained 50, 100, 150, and 200 nM poly(dT), lanes 5–8 contain G-rich WT, and lanes 9–12 G-mutant ODN, respectively. The positions of inter- and intramolecular G-quadruplex and the substrate is indicated on the right-hand side of the image. (C) Effect of KCl on the formation of G-quadruplex DNA. The CD spectral tracings of the indicated ODNs were obtained in the absence or presence of 120 mM KCl.