Semih Can Akıncılar1,2, Ekta Khattar1, Priscilla Li Shan Boon3, Bilal Unal1,2, Melissa Jane Fullwood3, Vinay Tergaonkar1,2,4*
1 Division of Cancer Genetics and Therapeutics, Laboratory of NFκB Signaling, Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research), Singapore 138673.
2 Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore 117597, Singapore
3 Cancer Science Institute, National University of Singapore, Singapore
4 Centre for Cancer Biology, University of South Australia and SA Pathology, Adelaide, Australia.
*Correspondence: Vinay TERGAONKAR, email@example.com,
Published online in Cancer Discovery on 16 September 2016.
Cancer-specific Tert promoter mutations (-146C>T and -124C>T) have been linked to reactivation of epigenetically silenced telomerase reverse transcriptase gene (Tert). Understanding how these single nucleotide alterations drive Tert reactivation is a fundamental unanswered question and is key for making successful therapeutics. We show that unlike on wild-type promoter, recruitment of transcription-factor GABPA specifically to mutant Tert promoters mediates long-range chromatin interaction, enrichment of active histone marks and hence drives Tert transcription. CRISPR mediated reversal of mutant Tert promoters, or deletion of its long-range interacting chromatin, abrogates GABPA binding, long-range interactions, leading to depletion of active histone marks, loss of Pol2 recruitment and suppression of Tert transcription. In contrast, de-novo introduction of Tert promoter mutation enables GABPA binding and upregulation of Tert via long-range interactions, acquisition of active histone marks and subsequent Pol2 recruitment. This study provides a unifying mechanistic insight into activation of mutant Tert promoters across various human cancers.
Figure 1: Mutant Tert promoter displays distinct long-range interactions
4C sequencing for long-range interactions of Tert promoter. Plot generated by r3CSeq of chromatin interactions of the Tert promoter for A375 and BLM cell lines. The top panel shows the Refseq genes in chromosome 5. The line plots show detected interactions 500 kb upstream and downstream of the Tert promoter. X axis indicates the distance from Tert promoter which was shown as ‘0’. Y axis was the read counts for each interaction. Different shades of red and blue color dots indicate positive interactions for A375 and BLM cells (average of two replicates) respectively. Darker color indicates more significant interactions according to q values indicated in the legend. P values were calculated by two tailed Student’s t test method.
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