Figure 1.

(A) Schematic representation of the human VEGF gene promoter region containing the polypurine/polypyrimidine tract proximally located at the transcription initiation site. Five G-repeats within this tract are indicated in open boxes (GR-1-GR-V). (B) Schematic representation of the hydrogen-bonded G-tetrad. (C) Schematic illustration of a major parallel G-quadruplex structure formed by the VEGF G-rich single strand in the presence of K⁺. The guanine residues involved in the formation of tetrads are underlined.