Functional loss of ATRX and telomerase activates Alternative Lengthening of Telomeres (ALT)
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE129448 | GEO | 2019/09/25
REPOSITORIES: GEO
Similar Datasets
Project description:DNA microarrays were used to define the transcriptional profiles of tumor samples to compare 12 high-grade pediatric osteosarcoma tumor samples on their ALT and ATRX status.
2022-07-12 | E-MTAB-11743 | biostudies-arrayexpress
Project description:Functional loss of ATRX and telomerase activates Alternative Lengthening of Telomeres (ALT)
| PRJNA531393 | ENA
Project description:<p>Many tumors maintain chromosome ends through a telomerase-independent, homologous recombination based mechanism called alternative lengthening of telomeres (ALT). While ALT occurs in only a subset of tumors, it is strongly associated with mutations in the genes encoding components of the histone H3.3 chaperone complex, ATRX and DAXX. To date the mechanistic role of ATRX and particularly DAXX mutations in potentiating ALT remains poorly understood. We identify an osteosarcoma cell line, G292, with a unique chromosomal translocation resulting in loss of DAXX function, while retaining functional ATRX. Using this distinctive resource, we demonstrate that introduction of wild type DAXX suppresses the ALT phenotype and restores localization of the ATRX/DAXX complex to PML bodies. This provides the first direct molecular evidence that ongoing DAXX deficiency is essential for maintenance of the ALT phenotype and highlights the potential for therapeutic targeting of this oncogenic pathway.</p>
| phs001495 | dbGaP
Project description:Alternative lengthening of telomeres (ALT) supports telomere maintenance and replicative immortality in around 10-15% of cancers, thus representing a compelling target for therapy.To identify anti-cancer drugs that can be repurposed as ALT-centered therapies, we performed for a compound library screen on isogenic cell lines that rely either on telomerase or ALT mechanisms. We validated candidates on a panel of ALT- vs. telomerase-positive sarcoma cells and assessed levels of extrachromosomal telomeric C-circles after drug treatment, as a bona fide marker of ALT activity. We identified a receptor tyrosine kinase inhibitor ponatinib that deregulated ALT mechanisms, increased telomeric replicative stress and induced telomeric dysfunction in ALT cells. Using a model of ALT sarcoma xenografts, we found that ponatinib targeted ALT-positive cells and mitigated telomere elongation in these tumors. To identify the mode of action of ponatinib on ALT, we performed RNA-sequencing and quantitative proteomic and phosphoproteomic analyses, and shortlisted candidates to test the effect of their loss on telomeric C-circle levels. We identified an ABL1-JNK-JUN signalling circuit to be inhibited by ponatinib and to have a role in suppressing extrachromosomal telomeric C-circle formation. Furthermore, transcriptome and interactome analyses of JUN suggested a role of JUN in DNA damage repair pathways, independently of its capacity as a transcription factor. These results were corroborated by new synergistic drug interactions between ponatinib and either DNA synthesis or repair inhibitors such as triciribine and KU-60019, respectively. Overall, we identified a novel signalling pathway impacting ALT which can be targeted by a clinically approved kinase inhibitor.
2023-02-20 | PXD037501 | Pride
Project description:Alternative lengthening of telomeres (ALT) supports telomere maintenance and replicative immortality in around 10-15% of cancers, thus representing a compelling target for therapy.To identify anti-cancer drugs that can be repurposed as ALT-centered therapies, we performed for a compound library screen on isogenic cell lines that rely either on telomerase or ALT mechanisms. We validated candidates on a panel of ALT- vs. telomerase-positive sarcoma cells and assessed levels of extrachromosomal telomeric C-circles after drug treatment, as a bona fide marker of ALT activity. We identified a receptor tyrosine kinase inhibitor ponatinib that deregulated ALT mechanisms, increased telomeric replicative stress and induced telomeric dysfunction in ALT cells. Using a model of ALT sarcoma xenografts, we found that ponatinib targeted ALT-positive cells and mitigated telomere elongation in these tumors. To identify the mode of action of ponatinib on ALT, we performed RNA-sequencing and quantitative proteomic and phosphoproteomic analyses, and shortlisted candidates to test the effect of their loss on telomeric C-circle levels. We identified an ABL1-JNK-JUN signalling circuit to be inhibited by ponatinib and to have a role in suppressing extrachromosomal telomeric C-circle formation. Furthermore, transcriptome and interactome analyses of JUN suggested a role of JUN in DNA damage repair pathways, independently of its capacity as a transcription factor. These results were corroborated by new synergistic drug interactions between ponatinib and either DNA synthesis or repair inhibitors such as triciribine and KU-60019, respectively. Overall, we identified a novel signalling pathway impacting ALT which can be targeted by a clinically approved kinase inhibitor.
2022-03-14 | PXD032188 | Pride
Project description:DAXX and ATRX are tumor suppressor proteins that form a complex with histone H3.3 chaperone and are frequently mutated in cancers with the alternative lengthening of telomeres (ALT), such as pediatric glioblastoma. Rapid loss of function of either DAXX or ATRX are not by themselves sufficient to induce the ALT phenotype. However, cells lacking DAXX or ATRX can be readily selected for ALT-like features. Here, we show that a key feature of ALT selected DAXX and ATRX null glioblastoma cells is the attenuation of p53 function. RNA-seq analysis of DAXX or ATRX null U87 glioblastoma cells with ALT-like features revealed that p53 pathway is among perturbed. ALT-selected DAXX and ATRX-null cells had aberrant response to DNA damaging agent etoposide. Both DAXX and ATRX-null ALT cells showed a loss of p53 binding at a subset of response elements. Complementation of DAXX null cells with wt DAXX rescued p53 binding and transcription, while the tumor associated mutation L130R, that disrupts ATRX binding, was incapable of rescuing p53 chromatin binding. We show that histone H3.3 binding is reduced in DAXX-null cells especially at subtelomeric p53 binding sites and telomere repeats. These findings indicate that DAXX and ATRX function to enable p53 chromatin binding through modulation of histone H3.3 binding, especially at sub-telomeric sites.
2022-07-19 | GSE207046 | GEO
Project description:DAXX and ATRX are tumor suppressor proteins that form a complex with histone H3.3 chaperone and are frequently mutated in cancers with the alternative lengthening of telomeres (ALT), such as pediatric glioblastoma. Rapid loss of function of either DAXX or ATRX are not by themselves sufficient to induce the ALT phenotype. However, cells lacking DAXX or ATRX can be readily selected for ALT-like features. Here, we show that a key feature of ALT selected DAXX and ATRX null glioblastoma cells is the attenuation of p53 function. RNA-seq analysis of DAXX or ATRX null U87 glioblastoma cells with ALT-like features revealed that p53 pathway is among perturbed. ALT-selected DAXX and ATRX-null cells had aberrant response to DNA damaging agent etoposide. Both DAXX and ATRX-null ALT cells showed a loss of p53 binding at a subset of response elements. Complementation of DAXX null cells with wt DAXX rescued p53 binding and transcription, while the tumor associated mutation L130R, that disrupts ATRX binding, was incapable of rescuing p53 chromatin binding. We show that histone H3.3 binding is reduced in DAXX-null cells especially at subtelomeric p53 binding sites and telomere repeats. These findings indicate that DAXX and ATRX function to enable p53 chromatin binding through modulation of histone H3.3 binding, especially at sub-telomeric sites.
2022-07-19 | GSE186442 | GEO
Project description:DAXX and ATRX are tumor suppressor proteins that form a complex with histone H3.3 chaperone and are frequently mutated in cancers with the alternative lengthening of telomeres (ALT), such as pediatric glioblastoma. Rapid loss of function of either DAXX or ATRX are not by themselves sufficient to induce the ALT phenotype. However, cells lacking DAXX or ATRX can be readily selected for ALT-like features. Here, we show that a key feature of ALT selected DAXX and ATRX null glioblastoma cells is the attenuation of p53 function. RNA-seq analysis of DAXX or ATRX null U87 glioblastoma cells with ALT-like features revealed that p53 pathway is among perturbed. ALT-selected DAXX and ATRX-null cells had aberrant response to DNA damaging agent etoposide. Both DAXX and ATRX-null ALT cells showed a loss of p53 binding at a subset of response elements. Complementation of DAXX null cells with wt DAXX rescued p53 binding and transcription, while the tumor associated mutation L130R, that disrupts ATRX binding, was incapable of rescuing p53 chromatin binding. We show that histone H3.3 binding is reduced in DAXX-null cells especially at subtelomeric p53 binding sites and telomere repeats. These findings indicate that DAXX and ATRX function to enable p53 chromatin binding through modulation of histone H3.3 binding, especially at sub-telomeric sites.
2022-07-19 | GSE186440 | GEO
Project description:Replicative senescence forms a major barrier to tumor progression. Cancer cells bypass this by using one of the two known telomere maintenance mechanisms: telomerase or the recombination-based alternative lengthening of telomeres (ALT) mechanism. The molecular details of ALT are currently poorly understood. We have previously shown that telomerase is actively repressed through complex networks of kinase, gene expression, and chromatin regulation. In this study, we aimed to gain further understanding of the role of kinases in the regulation of telomerase expression in ALT cells. Using a whole human kinome siRNA screen, we highlighted 106 kinases whose expression is linked to hTERT promoter activity. Network modeling of transcriptional regulation implicated c-Myc as a key regulator of the 106 kinase hits. Given our previous observations of lower c-Myc activity in ALT cells, we further explored its potential to regulate telomerase expression in ALT. We found increased c-Myc binding at the hTERT promoter in telomerase-positive compared with ALT cells, although no expression differences in c-Myc, Mad, or Max were observed between ALT and telomerase-positive cells that could explain decreased c-Myc activity in ALT. Instead, we found increased expression of the c-Myc competitive inhibitor TCEAL7 in ALT cells and tumors and that alteration of TCEAL7 expression levels in ALT and telomerase-positive cells affects hTERT expression. Lower c-Myc activity in ALT may therefore be obtained through TCEAL7 regulation. Thus, TCEAL7 may present an interesting novel target for cancer therapy, which warrants further investigation.
2010-05-04 | GSE17118 | GEO
Project description:Alternative Lengthening of Telomeres (ALT) is an aberrant DNA recombination pathway which grants replicative immortality to approximately 10% of all cancers. Despite this high prevalence of ALT in cancer, the mechanism and genetics by which cells activate this pathway remain incompletely understood. A major challenge in dissecting the events that initiate ALT is the extremely low frequency of ALT induction in human cell systems. Guided by the genetic lesions that have been associated with ALT from cancer sequencing studies, we genetically engineered primary human pluripotent stem cells to deterministically induce ALT upon differentiation. Using this genetically defined system, we demonstrate that disruption of the p53 and Rb pathways in combination with ATRX loss-of-function is sufficient to induce all hallmarks of ALT and results in functional immortalization in a cell type-specific manner. We further demonstrate that ALT can be induced in the presence of telomerase, is neither dependent on telomere shortening nor crisis, but is rather driven by continuous telomere instability triggered by the induction of differentiation in ATRX-deficient stem cells.
2023-02-21 | GSE212809 | GEO