Dimeric G-quadruplex DNA Structure in the Proximal Promoter of VEGFR-2 Reveals a New Drug Target to Inhibit Tumor Angiogenesis

Vascular endothelial growth factor(VEGF)regulates tumor angiogenesis,which is active on the endothelium via VEGF receptor 2(VEGFR-2).The proximal promoter region of VEGFR-2(termed as VEGFR-2 DNA)is guanine-rich,forming G-quadruplex(G4)structures.Here,we demonstrate that VEGFR-2 DNA consists of one symmetrically dimeric 14-mer G4-DNA and one 12-mer sequence-palindromic dsDNA.This G4-DNA adopts an unprecedented folding with five stacked tetrads linked by four broken strands.Its 5’-end part contains an A-tetrad A^(1)•A^(4)•A^(1’)•A^(4’)and one G-tetrad G^(3)•G^(5)•G^(3’)•G^(5’)with two V-shaped loops and two one-nt edge-type loops.Its 3’-end part includes three G-tetrads G^(10)•G^(6)•G^(10’)•G^(6’),G^(11)•G^(7)•G^(11’)•G^(7’)(central)and G^(12)•G^(8)•G^(12’)•G^(8’)spanned by two double-chain-reversal one-nt(C^(9)or C^(9’))loops.Bases G^(13)and G^(13’)stack with G-tetrad G^(12)•G^(8)•G^(12’)•G^(8’).These characteristics make this G4-DNA more stable than reported VEGFR-17T G4 structure.The dsDNA connects with G4-DNA without any interactions,generating a linear assembly with G4-DNA structural bulges.These studies uncover new structural features of VEGFR-2 DNA as a potential drug target by inhibiting VEGFR-2 expression,thereby tumor angiogenesis.