GABP determines the epigenetic status of mutant TERT promoter
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE77265 | GEO | 2017/02/27
SECONDARY ACCESSION(S): PRJNA309931
REPOSITORIES: GEO
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Project description:Using microcell-mediated chromosome transfer (MMCT) into the mouse melanoma cell line, B16F10, we have previously found that human chromosome 5 carries a gene, or genes, that can negatively regulate TERT expression. To identify the gene responsible for the regulation of TERT transcription, we performed cDNA microarray analysis using parental B16F10 cells, telomerase negative B16F10 microcell hybrids with a human chromosome 5 (B16F10MH5), and its revertant clones (MH5R) with reactivated telomerase. Here we report the identification of PITX1, whose restoration leads to the downregulation of mouse tert (mtert) transcription, as a TERT suppressor gene. Additionally, both human TERT (hTERT) and mouse TERT (mtert) promoter activity can be suppressed by PITX1. We showed that three and one binding sites, respectively, within the hTERT and mtert promoters that express a unique conserved region are responsible for the transcriptional activation of TERT. Furthermore, we showed that PITX1 binds to the TERT promoter both in vitro and in vivo. Thus, PITX1 suppresses TERT transcription through direct binding to the TERT promoter, which ultimately regulates telomerase activity. We transferred intact human chromosome 5 into mouse melanoma B16F10 cells by microcell fusion. The microcell hybrids (MH5) exhibited suppression of telomerase, we also obtained revertant clones (MH5R) in which telomerase is reactivated. To identify the differentially expressed genes on human chromosome 5, we performed expression microarray analysis using these two clones and parental B16F10 cells.
2010-09-10 | E-GEOD-23216 | biostudies-arrayexpress
Project description:Over 50 types of cancer acquire TERT promoter mutations. These single point mutations reactivate telomerase, allowing for indefinite maintenance of telomere length and enabling cellular immortalization. The transcription factor binding site created by the point mutations specifically recruit the ETS factor GABP, a multimeric transcription factor composed of the GABPα and GABPβ subunits. GABP can form two functionally independent transcription factor species – a dimer or a tetramer – depending on which of the structurally distinct GABPβ isoforms is incorporated into the complex. In this study, we show that genetic disruption of GABPβ1L, a tetramer forming isoform of GABPβ that is dispensable in normal development, results in TERT silencing in a TERT promoter mutation dependent manner. Failure to activate TERT expression by GABPβ1L culminates in telomere dysfunction, DNA damage, and mitotic cell death exclusively in TERT promoter mutant cells. Furthermore, exogenous expression of TERT is sufficient to prevent telomere degradation and loss of cell viability in GABPβ1L-reduced lines bearing the mutant TERT promoter. Orthotopic injection of tetramer-deficient mutant TERT promoter GBM cells rendered lower tumor burden and prolonged the overall survival of the tumor-bearing mice. These results highlight the potentially widespread role of GABPB1L in enabling replicative immortality of TERT promoter cancers.
| EGAS00001002582 | EGA
Project description:Reactivation of telomerase reverse transcriptase (TERT) expression enables cells to overcome replicative senescence and escape apoptosis, fundamental steps in the initiation of human cancer. Multiple cancer types, including up to 83% of glioblastomas (GBM), harbor highly recurrent TERT promoter mutations of unknown function but specific to two nucleotide positions. We identify the functional consequence of these mutations in GBM to be recruitment of the multimeric GABP transcription factor specifically to the mutant promoter. Allelic recruitment of GABP is consistently observed across four cancer types, highlighting a shared mechanism underlying TERT reactivation. Tandem flanking native ETS motifs critically cooperate with these mutations to activate TERT, likely by facilitating GABP heterotetramer binding. GABP thus directly links TERT promoter mutations to aberrant expression in multiple cancers.
| EGAS00001001242 | EGA
Project description:Using microcell-mediated chromosome transfer (MMCT) into the mouse melanoma cell line, B16F10, we have previously found that human chromosome 5 carries a gene, or genes, that can negatively regulate TERT expression. To identify the gene responsible for the regulation of TERT transcription, we performed cDNA microarray analysis using parental B16F10 cells, telomerase negative B16F10 microcell hybrids with a human chromosome 5 (B16F10MH5), and its revertant clones (MH5R) with reactivated telomerase. Here we report the identification of PITX1, whose restoration leads to the downregulation of mouse tert (mtert) transcription, as a TERT suppressor gene. Additionally, both human TERT (hTERT) and mouse TERT (mtert) promoter activity can be suppressed by PITX1. We showed that three and one binding sites, respectively, within the hTERT and mtert promoters that express a unique conserved region are responsible for the transcriptional activation of TERT. Furthermore, we showed that PITX1 binds to the TERT promoter both in vitro and in vivo. Thus, PITX1 suppresses TERT transcription through direct binding to the TERT promoter, which ultimately regulates telomerase activity.
2010-09-10 | GSE23216 | GEO
Project description:Transcriptional re-activation of hTERT is the limiting step in tumorigenesis. While mutations in hTERT promoter seen in 19% of all cancers are recognized as key drivers of hTERT reactivation, mechanisms by which the wildtype hTERT (WT-hTERT) promoter is reactivated, as observed in the majority of cancers, remain unknown. We report that unlike with the mutant-hTERT promoters, a T-INT2 (Tert INTeracting region 2) region located ~120kb upstream of the hTERT proximal promoter is essential to uniquely reactivate the WT-hTERT promoter, via long-range chromatin interactions. Unlike mutant-hTERT promoters, which are driven by GABPa/b tetramers tethered between T-INT1 (Tert-INTeracting-region 1) and de-novo ETS sites created by promoter mutations, WT-hTERT promoter firing is initiated by 2 events a) elevated JunD mediated recruitment of CTCF and b) β-catenin and CBP mediated recruitment of Sp1 tetramers between T-INT2 and WT-hTERT proximal-promoter, leading to chromatin-openness, pol2 recruitment and productive transcription.
2023-01-08 | GSE163070 | GEO
Project description:Transcriptional re-activation of hTERT is the limiting step in tumorigenesis. While mutations in hTERT promoter seen in 19% of all cancers are recognized as key drivers of hTERT reactivation, mechanisms by which the wildtype hTERT (WT-hTERT) promoter is reactivated, as observed in the majority of cancers, remain unknown. We report that unlike with the mutant-hTERT promoters, a T-INT2 (Tert INTeracting region 2) region located ~120kb upstream of the hTERT proximal promoter is essential to uniquely reactivate the WT-hTERT promoter, via long-range chromatin interactions. Unlike mutant-hTERT promoters, which are driven by GABPa/b tetramers tethered between T-INT1 (Tert-INTeracting-region 1) and de-novo ETS sites created by promoter mutations, WT-hTERT promoter firing is initiated by 2 events a) elevated JunD mediated recruitment of CTCF and b) β-catenin and CBP mediated recruitment of Sp1 tetramers between T-INT2 and WT-hTERT proximal-promoter, leading to chromatin-openness, pol2 recruitment and productive transcription.
2023-01-08 | GSE163069 | GEO
Project description:Point mutations within the TERT promoter are the most common recurrent somatic non-coding mutation identified across different cancer types, including glioblastoma, melanoma, hepatocellular carcinoma and bladder cancer. They are most abundant at C146T and C124T and more rare at A57C, with the latter originally described as a familial case but subsequently shown also to occur somatically. All three mutations create de novo ETS (E-twenty-six specific) binding sites and result in the reactivation of the TERT gene, 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 a an A57C-specific binder and ZNF148 as a TERT WT binder that is excluded from the TERT promoter by the C124T allele. Both proteins are activating transcription factors that bind specifically to the A57C and wildtype (at position 124) TERT promoter sequence in corresponding cell lines and upregulate TERT transcription and telomerase activity.
2023-11-04 | PXD037776 | Pride
Project description:Mutations in the promoter of the telomerase reverse transcriptase (TERT) gene are the paradigm of a cross-cancer alteration in a non-coding region. TERT promoter mutations (TPMs) are biomarkers of poor prognosis in cancer, including thyroid tumors. TPMs enhance TERT transcription, which is otherwise silenced in adult tissues, thus reactivating a bona fide oncoprotein. To study TERT deregulation and its downstream consequences, we generated a Tert mutant promoter mouse model via CRISPR/Cas9 engineering of the murine equivalent locus (Tert-123C>T) and crossed it with thyroid-specific BrafV600E-mutant mice. We also employed an alternative model of Tert overexpression (K5-Tert). Whereas all BrafV600E animals developed well-differentiated papillary thyroid tumors, 29% and 36% of BrafV600E+Tert-123C>T and BrafV600E+K5-Tert mice progressed to poorly differentiated cancers at week 20, respectively. Tert-upregulated tumors showed increased mitosis and necrosis in areas of solid growth, and older animals displayed anaplastic-like features, i.e., spindle cells and macrophage infiltration. Murine Tert promoter mutation increased Tert transcription in vitro and in vivo, but temporal and intra-tumoral heterogeneity was observed. RNA-sequencing of thyroid tumor cells showed that processes other than the canonical Tert-mediated telomere maintenance role operate in these specimens. Pathway analysis showed that MAPK and PI3K/AKT signaling, as well as processes not previously associated with this tumor etiology, involving cytokine and chemokine signaling, were overactivated. These models constitute useful pre-clinical tools to understand the cell-autonomous and microenvironment-related consequences of Tert-mediated progression in advanced thyroid cancers and other aggressive tumors carrying TPMs. Implications: Telomerase-driven cancer progression activates pathways that can be dissected and perhaps therapeutically exploited.
2023-08-01 | GSE227539 | GEO
Project description:Human telomerase reverse transcriptase (hTERT) is a rate-limiting catalytic subunit of the enzyme telomerase, which plays a central role in maintaining replicative immortality in normal stem cells and many cancer cells. Mostly silenced in normal somatic cells, hTERT is reactivated in cancer commonly through highly recurrent hot spot point mutations in the hTERT promoter. Bladder cancer has a 60-70% hTERT promoter mutation prevalence, commonly at -124 bp from the translation start site, and this is associated with increased hTERT expression and poor patient prognosis. Identifying targetable signaling pathways that drive hTERT transcription from the mutant promoter could lead to therapies with reduced effects on normal progenitors. Here we describe a new platform that probes endogenous hTERT regulation by allele-specific insertion of GFP at either wild-type or mutant promoter allele within human bladder cancer cells harboring a heterozygous mutation. Using cells expressing the GFP-hTERT fusion protein, we performed a pooled CRISPR-Cas9 Kinome KO genetic screen to identify regulators of mutant hTERT promoter activity. We identified TRIM28 as an activator and TRIM24 as a suppressor of hTERT expression. Similar to hTERT, TRIM28 expression stratifies patient outcome and inhibits promotes cell growth both in vitro and in vivo, supporting their clinical relevance. TRIM28 and TRIM24 get recruited to the mutated promoter through GABPA, where TRIM24 interacts with TRIM28 and inhibits its activity as a transcriptional activator. TRIM28 phosphorylation causes its release from TRIM24 and activates hTERT transcription. mTOR phosphorylates TRIM28 through the mTORC1 complex leading to hTERT expression, while mTORC1 inhibition with rapamycin analog Ridaforolimus suppresses the phosphorylation and promoter binding of TRIM28, resulting in reduced hTERT expression and lower cell viability. This study uses a bespoke platform to identify a novel therapeutically tractable regulatory pathway for cancers harboring mutant hTERT promoters.
2021-08-06 | GSE181461 | GEO
Project description:Hotspot mutations in the core promoter region of the telomerase reverse transcriptase (TERT) gene have been well established to associate with aggressive clinical characteristics, radioiodine refractory, tumor recurrence and mortality in thyroid cancer. Several E-twenty-six (ETS) transcription factors were reported to selectively bound to the mutant TERT promoter and activated TERT expression. In this study we aimed to investigate whether TERT promoter mutations confer sensitivity to ETS inhibitor YK-4-279 in thyroid cancer cells and whether this inhibitor could be served as a potential therapeutic agent for thyroid cancer. In vitro assays showed that YK-4-279 treatment sharply suppressed cell viability, colony formation, migration and invasion, as well as induced cell cycle arrest and apoptosis in a panel of thyroid cancer cells. The cell viability after YK-4-279 treatment were similar between cell lines harboring mutant and wild-type TERT promoter. Furthermore, YK-4-279 treatment reduced both luciferase activity and mRNA expression of TERT independent of TERT promoter mutation status. Data from RNA-seq further revealed that YK-4-279 significantly affected biological processes including DNA replication and cell cycle. Reduced DNA helicase activity and decreased expression of several helicase genes were observed after YK-4-279 treatment. Moreover, YK-4-279 significantly inhibited tumor growth and induced apoptosis in a xenograft mice model. Thus, ETS inhibitor YK-4-279 suppressed TERT expression and conferred anti-tumor activity in a TERT promoter mutation-independent manner, and it could be a potential agent for the treatment of advanced thyroid cancers.
2021-04-06 | GSE171473 | GEO