Functional loss of ATRX and telomerase activates Alternative Lengthening of Telomeres (ALT)
Ontology highlight
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:Alterations to chromatin modifiers, such as the inactivating mutations in the ATRX-DAXX chromatin remodeling/histone H3.3 deposition complex, are implicated as drivers of the cancer-specific Alternative Lengthening of Telomeres (ALT) pathway. Prior studies revealed that HIRA adapts to compensate for ATRX-DAXX loss to sustain ALT cancer cell survival. However, the specific mechanisms underlying HIRA’s ability to rescue telomeres from the consequences of ATRX-DAXX loss remain unclear. Here, using ATAC-seq and CUT&RUN, we demonstrate that HIRA-mediated deposition of new H3.3 is essential to maintain chromatin accessibility and to prevent the detrimental accumulation of nucleosome-free single-stranded DNA (ssDNA) at telomeres in ATRX-deficient ALT cancer cells. We provide evidence that the timely deposition of new H3.3 by HIRA and interacting partners UBN1 and UBN2 is crucial to prevent unwarranted TERRA R-loop formation and transcription-replication conflicts (TRCs) at telomeres. Furthermore, we determined that the delivery of H3.3 to telomeric chromatin by HIRA may link the phosphorylation of an H3.3-specific amino acid, serine 31, by Chk1 with mechanisms that promote productive ALT. Therefore, these studies identify a role for HIRA-mediated histone H3.3 deposition in TERRA R-loop homeostasis that we propose is essential for ensuring the survival of ALT cancer cells where the ATRX-DAXX complex is activated.
2024-10-21 | GSE269268 | GEO
Project description:Alterations to chromatin modifiers, such as the inactivating mutations in the ATRX-DAXX chromatin remodeling/histone H3.3 deposition complex, are implicated as drivers of the cancer-specific Alternative Lengthening of Telomeres (ALT) pathway. Prior studies revealed that HIRA adapts to compensate for ATRX-DAXX loss to sustain ALT cancer cell survival. However, the specific mechanisms underlying HIRA’s ability to rescue telomeres from the consequences of ATRX-DAXX loss remain unclear. Here, using ATAC-seq and CUT&RUN, we demonstrate that HIRA-mediated deposition of new H3.3 is essential to maintain chromatin accessibility and to prevent the detrimental accumulation of nucleosome-free single-stranded DNA (ssDNA) at telomeres in ATRX-deficient ALT cancer cells. We provide evidence that the timely deposition of new H3.3 by HIRA and interacting partners UBN1 and UBN2 is crucial to prevent unwarranted TERRA R-loop formation and transcription-replication conflicts (TRCs) at telomeres. Furthermore, we determined that the delivery of H3.3 to telomeric chromatin by HIRA may link the phosphorylation of an H3.3-specific amino acid, serine 31, by Chk1 with mechanisms that promote productive ALT. Therefore, these studies identify a role for HIRA-mediated histone H3.3 deposition in TERRA R-loop homeostasis that we propose is essential for ensuring the survival of ALT cancer cells where the ATRX-DAXX complex is activated.
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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.
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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.
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