A. A schematic representation of the HIF-1α proximal promoter demonstrating the position of the poly-purine/poly-pyrimidine (pPu/pPy) tract relative to the transcriptional start site. The six guanine/cytosine runs (I-V) are underlined in the base composition of the pPu/pPy tract. B. Colored boxes represent transcription factor binding sites such as HIF-1α to the hypoxia response element (HRE), specific protein 1 (Sp1) and cAMP response element binding (CREB). The structure and base pairing of guanine tetrads are represented by red square planes, which form the previously characterized HIF-1α intramolecular G-quadruplex [20]. Red, green and yellow circles represent the nucleobases guanine, adenine and cytosine, respectively.
