FOS bound to 5′-UTR of GABPB and upregulated mutant TERT expression. a Diagrammatic illustration of the putative FOS- and MYC-binding sites in the 5′-UTR of GABPB identified by bioinformatics analyses. The predicted palindromic FOS consensus binding site (5′-TGACTCA-3′) and the canonical MYC binding site (5′-CATGTG-3′) located at +222 to +228 and +238 to +243, downstream of the transcriptional start site, respectively. b GABPB 5′-UTR region-luciferase-reporter assays for the wild-type and artificially-induced mutated putative FOS- and MYC-binding sites. c ChIP assay for FOS and MYC occupancy at the 5′-UTR of GABPB in K1 and A375 cells. Pol II and IgG were used for positive and negative controls, respectively. d Western blotting analyses of GABPB, MYC, FOS, and beta-actin in K1 cells with stable FOS or MYC knockdown. e TERT promoter-luciferase reporter assays in K1 cells with stable FOS knockdown. f Western blotting analyses for TERT, FOS, and beta-actin in K1, A375 and WRO cells with or without stable FOS knockdown. *P < 0.05, **P < 0.01, by two-tailed Student’s t test. n.s. not significant. All values represent the average ± standard deviation (SD) of triplicate samples, and similar results were obtained in three independent experiments