E4F1 and ZNF148 are transcriptional activators of the A57C and wildtypeTERTpromoter

Abstract

ABSTRACTPoint mutations within theTERTpromoter are the most recurrent somatic non-coding mutations identified across different cancer types, including glioblastoma, melanoma, hepatocellular carcinoma, and bladder cancer. They are most abundant at C146T and C124T and rarer at A57C, with the latter originally described as a familial case but subsequently shown also to occur somatically. All three mutations createde novoETS (E-twenty-six specific) binding sites and result in the reactivation of theTERTgene, allowing cancer cells to achieve replicative immortality. Here, we employed a systematic proteomics screen to identify transcription factors preferentially binding to the C146T, C124T and A57C mutations. While we confirmed binding of multiple ETS factors to the mutant C146T and C124T sequences, we identified E4F1 as an A57C-specific binder and ZNF148 as aTERTWT binder that is excluded from theTERTpromoter by the C124T allele. Both proteins are activating transcription factors that bind specifically to the A57C and wildtype (at position 124)TERTpromoter sequence in corresponding cell lines and upregulateTERTtranscription and telomerase activity. Our work describes new regulators of TERT gene expression with possible roles in cancer.