Fig. 8

Hypoxia-induced HIF1α-SP1 interaction disrupts the circ-0001875/ miR-31-5p/SP1/AluSq regulatory loop. a Schematic diagram illustrates Alu-mediated RNA circularization and suppression when SP1 binds to AluSq element. b The sequences and base pairing condition of AluSq and AluSz6 and the SP1 binding sites on AluSq sequences are listed. c RIP assays using SP1 antibody were performed to examine interactions with the AluSq wild-type (AluSq WT) and AluSq 150–154 nt mutant-type (AluSq MUT (150–154)). d–e Relative expression of circ-0001875 and FAM120A mRNA in A549 and H1299 cells transfected with the indicated vectors or siRNAs was determined by RT-qPCR. f Western blot analysis of HIF1α expression in cells under hypoxia or normoxia. g circ-0001875 expression under hypoxia and normoxia analyzed by RT-qPCR. h-i CoIP analysis of the HIF1α-SP1 interaction in cells treated as indicated. j Relative expression of HIF1α in A549 and H1299 cells transfected with the short hairpin RNA of HIF1α (si-HIF1α) and determined by RT-qPCR. k Relative expression of circ-0001875 after transfected with si-HIF1α under hypoxia condition. l RIP assays using a SP1 antibody were performed to examine interactions with AluSq WT after NSCLC cells were treated with hypoxia. Data are shown as the means ± SD. *p < 0.05, **p < 0.01, ***p < 0.001