Abstract
Background: Chief among mechanisms of telomerase reverse transcriptase (TERT) reactivation is the appearance of mutations in the TERT promoter. The two main TERT promoter mutations are C>T transitions located −146C>T and −124C>T upstream from the translational start site. They generate a novel Ets/TCF binding site. Both mutations are mutually exclusive and −124C>T is strikingly overrepresented in most cancers. We investigated whether this mutational bias and mutual exclusion could be due to transcriptional constraints. Methods: We compared sense and antisense transcription of a panel of TERT promoter-luciferase vectors harboring the −124C>T and -146C>T mutations alone or together. lncRNA TAPAS levels were measured by RT-PCR. Results: Both mutations generally increased TERT transcription by 2–4-fold regardless of upstream and downstream regulatory elements. The double mutant increased transcription in an additive fashion, arguing against a direct transcriptional constraint. The −146C>T mutation, alone or in combination with −124C>T, also unleashed antisense transcription. In line with this finding, lncRNA TAPAS was higher in cells with mutated TERT promoter (T98G and U87) than in cells with wild-type promoter, suggesting that lncRNA TAPAS may balance the effect of TERT promoter mutations. Conclusions: −146C>T and −124C>T TERT promoter mutations increase TERT sense and antisense transcription, and the double mutant features higher transcription levels. Increased antisense transcription may contain TERT expression within sustainable levels.
Highlights
Telomeres are DNA–protein complexes which act as protective caps for chromosomal ends
The double mutant enabled significantly higher transcription levels compared with we investigated whether telomerase reverse transcriptase (TERT) promoter mutations impacted antisense tranthe wt TERT promoter (p < 0.01 or p < 0.001) and compared to each of the single mutants scription from the TERT promoter, introducing the −146C>T and −124C>T mutations alone for all constructs in both cell lines (Figure 2A,B)
Our results indicate that the double mutant confers a transcriptional advantage over the single mutants and argue against a transcriptional constraint being the main reason for the mutual exclusion of TERT promoter mutations in vivo
Summary
Telomeres are DNA–protein complexes which act as protective caps for chromosomal ends They consist of tandem repeats of the sequence TTAGGG bound by Shelterin enzymes. They shield chromosomal ends from inappropriate DNA damage responses, end-to-end fusion events and erosion, maintaining genomic integrity [1,2,3,4]. The two main TERT promoter mutations are C>T transitions located −146C>T and −124C>T upstream from the translational start site. They generate a novel Ets/TCF binding site. Both mutations are mutually exclusive and −124C>T is strikingly overrepresented in most cancers.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
