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. 2020 May 13;117(21):11409–11420. doi: 10.1073/pnas.1912355117

Fig. 6.

Fig. 6.

APE1 regulates G4-mediated Myc gene expression. (A) WT MYC G4 promoter luciferase reporter (MYC-WT) and pRL-TK−renilla luciferase were cotransfected in HCT116 cells transiently expressing siCtl or siAPE1 or constitutively expressing APE1shRNA. Forty-eight hours after transfection, cells were treated with 1 mM H2O2 for 1 h, and luciferase activity was measured and normalized with renilla luciferase. (Insets) The level of APE1 in these cell extracts was examined by Western blot analysis with α-APE1 and α-HSC70. (B) The sequence of the G4-forming Nuclease Hypersensitive element III1 (NHEIII1) element of the c-MYC gene. Bases are numbered according to the sequence of the NHEIII1. Two alternative G4 folding patterns (MYC-1245 and MYC-2345) of NHEIII1 are shown. (C) MYC–WT promoter luciferase reporters or MYC harboring a G to A mutation of the 12th base (MYC-G12A) and 18th base (MYC-G18A) were transfected in Dox-inducible HCT116APE1shRNA cells. Firefly luciferase activity was measured and normalized with renilla luciferase activity. (Inset) The level of APE1 knockdown in these cell extracts was examined by Western blot analysis with α-APE1 and α-HSC70. The P value was determined using an unpaired Student’s t test (****P < 0.0001, ***P < 0.001, **P < 0.01, n.s. (nonsignificant) = P > 0.05). Error bars denote +SD.