Expression of telomerase prevents ALT and maintains telomeric heterochromatin in juvenile brain tumors.
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA554016 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR9669990.fastq.gz | Fastqsanger.gz | |||
| SRR9669991.fastq.gz | Fastqsanger.gz | |||
| SRR9669992.fastq.gz | Fastqsanger.gz | |||
| SRR9669993.fastq.gz | Fastqsanger.gz | |||
| SRR9669988.fastq.gz | Fastqsanger.gz |
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Project description:The up-regulation of a telomere maintenance mechanism (TMM) is an essential step in cancer progression to escape dysfunctional telomeres, senescence and apoptosis. Paediatric brain tumors frequently exhibit Alternative Lengthening of Telomere (ALT) as active TMM, but the mechanisms involved in the induction of ALT in brain tumor cells are not clear. Here, we report a model of juvenile zebrafish brain tumor that progressively develops ALT. We discovered that reduced expression of tert and increase in Terra expression precedes ALT development. Additionally, tumors show persistent telomeric DNA damage and loss of heterochromatin marks. Comparative analysis of gene expression after the rescue of ALT with telomerase and analysis of telomerase positive paediatric brain cancers showed normalization of telomeric heterochromatin and maintenance of telomere length, with reduced expression of genes of the pre-replicative complex as hallmark. Thus our study identifies telomere maintenance mechanisms as major drivers of DNA replication and chromatin status at telomeres in brain cancers.
2022-07-01 | GSE134135 | GEO
Project description:Telomere is a highly refined system for maintaining the stability of linear chromosomes. Most telomeres rely on simple repetitive sequences and telomerase enzymes, but in some species or telomerase-defective situations, alternative telomere lengthening (ALT) mechanism is utilized to protect chromosomal ends. Telomere loss can induce telomere recombination by which specific sequences can be recruited into telomeres. However, canonical telomeric repeat-based telomeres have been found in mammals. Here, we show that mammalian telomeres can also be completely reconstituted using a non-telomeric unique sequence. We found that a specific subtelomeric element, named as mouse template for ALT (mTALT), is utilized for repairing telomeric DNA damage and composing new telomeric sequences in mouse embryonic stem cells. We found a high-level of non-coding mTALT transcript despite the heterochromatic nature of mTALT-based telomere. After ALT activation, the increased HMGN1, a non-histone chromosomal protein, contributed to maintaining telomere stability by regulating telomeric transcriptions. Our findings reveal novel molecular features of potential telomeric sequences which can reconstitute telomeres during cancer formation and evolution.
2020-07-17 | MSV000085772 | MassIVE
Project description:Epigenetic control of telomeric RNA maintains heterochromatin in telomerase-driven cancers
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Project description:Tumor heterogeneity presents a major clinical challenge. Reactivation of telomerase (hTERT) is a near-universal hallmark of cancer, yet direct inhibition of hTERT has shown limited therapeutic benefit. To uncover tractable telomerase-related vulnerabilities, we applied a synthetic dosage lethality (SDL) strategy to identify genes required only when hTERT is overexpressed. We performed genome-wide CRISPR/Cas9 and shRNA screens across multiple isogenic cell line pairs differing in hTERT expression. From these datasets, 100 high-confidence candidates were prioritized and validated using an arrayed in vitro CRISPR screen and a pooled in vivo CRISPR screen across diverse cancer models, non-malignant cells, and patient-derived organoids. Through this pipeline, we identified FTSJ3, an RNA 2′-O-methyltransferase, as a top SDL target of hTERT. Depletion of FTSJ3 selectively impaired the viability of hTERT-positive cancer cells while sparing normal cells. Mechanistically, FTSJ3 installs 2′-O-methylation on the telomeric RNA TERRA, a modification essential for TERRA stability and function. Loss of FTSJ3 destabilizes TERRA, disrupts recruitment of the histone methyltransferase SUV39H1, and diminishes H3K9 trimethylation and HP1 assembly at sub-telomeric regions. This breakdown of repressive telomeric chromatin leads to genome instability and apoptosis specifically in hTERT-positive cells. These findings highlight SDL as a powerful strategy for uncovering telomerase-dependent liabilities and establish FTSJ3 as a central regulator of telomere stability in telomerase-active cancers. Targeting FTSJ3 enzymatic activity offers a promising therapeutic entry point, acting upstream of TERRA to eliminate telomerase-driven malignancies selectively.
2026-03-18 | GSE211312 | GEO
Project description:Tumor heterogeneity presents a major clinical challenge. Reactivation of telomerase (hTERT) is a near-universal hallmark of cancer, yet direct inhibition of hTERT has shown limited therapeutic benefit. To uncover tractable telomerase-related vulnerabilities, we applied a synthetic dosage lethality (SDL) strategy to identify genes required only when hTERT is overexpressed. We performed genome-wide CRISPR/Cas9 and shRNA screens across multiple isogenic cell line pairs differing in hTERT expression. From these datasets, 100 high-confidence candidates were prioritized and validated using an arrayed in vitro CRISPR screen and a pooled in vivo CRISPR screen across diverse cancer models, non-malignant cells, and patient-derived organoids. Through this pipeline, we identified FTSJ3, an RNA 2′-O-methyltransferase, as a top SDL target of hTERT. Depletion of FTSJ3 selectively impaired the viability of hTERT-positive cancer cells while sparing normal cells. Mechanistically, FTSJ3 installs 2′-O-methylation on the telomeric RNA TERRA, a modification essential for TERRA stability and function. Loss of FTSJ3 destabilizes TERRA, disrupts recruitment of the histone methyltransferase SUV39H1, and diminishes H3K9 trimethylation and HP1 assembly at sub-telomeric regions. This breakdown of repressive telomeric chromatin leads to genome instability and apoptosis specifically in hTERT-positive cells. These findings highlight SDL as a powerful strategy for uncovering telomerase-dependent liabilities and establish FTSJ3 as a central regulator of telomere stability in telomerase-active cancers. Targeting FTSJ3 enzymatic activity offers a promising therapeutic entry point, acting upstream of TERRA to eliminate telomerase-driven malignancies selectively.
2026-03-18 | GSE279000 | GEO
Project description:Tumor heterogeneity presents a major clinical challenge. Reactivation of telomerase (hTERT) is a near-universal hallmark of cancer, yet direct inhibition of hTERT has shown limited therapeutic benefit. To uncover tractable telomerase-related vulnerabilities, we applied a synthetic dosage lethality (SDL) strategy to identify genes required only when hTERT is overexpressed. We performed genome-wide CRISPR/Cas9 and shRNA screens across multiple isogenic cell line pairs differing in hTERT expression. From these datasets, 100 high-confidence candidates were prioritized and validated using an arrayed in vitro CRISPR screen and a pooled in vivo CRISPR screen across diverse cancer models, non-malignant cells, and patient-derived organoids. Through this pipeline, we identified FTSJ3, an RNA 2′-O-methyltransferase, as a top SDL target of hTERT. Depletion of FTSJ3 selectively impaired the viability of hTERT-positive cancer cells while sparing normal cells. Mechanistically, FTSJ3 installs 2′-O-methylation on the telomeric RNA TERRA, a modification essential for TERRA stability and function. Loss of FTSJ3 destabilizes TERRA, disrupts recruitment of the histone methyltransferase SUV39H1, and diminishes H3K9 trimethylation and HP1 assembly at sub-telomeric regions. This breakdown of repressive telomeric chromatin leads to genome instability and apoptosis specifically in hTERT-positive cells. These findings highlight SDL as a powerful strategy for uncovering telomerase-dependent liabilities and establish FTSJ3 as a central regulator of telomere stability in telomerase-active cancers. Targeting FTSJ3 enzymatic activity offers a promising therapeutic entry point, acting upstream of TERRA to eliminate telomerase-driven malignancies selectively.
2026-03-18 | GSE223716 | GEO
Project description:Tumor heterogeneity presents a major clinical challenge. Reactivation of telomerase (hTERT) is a near-universal hallmark of cancer, yet direct inhibition of hTERT has shown limited therapeutic benefit. To uncover tractable telomerase-related vulnerabilities, we applied a synthetic dosage lethality (SDL) strategy to identify genes required only when hTERT is overexpressed. We performed genome-wide CRISPR/Cas9 and shRNA screens across multiple isogenic cell line pairs differing in hTERT expression. From these datasets, 100 high-confidence candidates were prioritized and validated using an arrayed in vitro CRISPR screen and a pooled in vivo CRISPR screen across diverse cancer models, non-malignant cells, and patient-derived organoids. Through this pipeline, we identified FTSJ3, an RNA 2′-O-methyltransferase, as a top SDL target of hTERT. Depletion of FTSJ3 selectively impaired the viability of hTERT-positive cancer cells while sparing normal cells. Mechanistically, FTSJ3 installs 2′-O-methylation on the telomeric RNA TERRA, a modification essential for TERRA stability and function. Loss of FTSJ3 destabilizes TERRA, disrupts recruitment of the histone methyltransferase SUV39H1, and diminishes H3K9 trimethylation and HP1 assembly at sub-telomeric regions. This breakdown of repressive telomeric chromatin leads to genome instability and apoptosis specifically in hTERT-positive cells. These findings highlight SDL as a powerful strategy for uncovering telomerase-dependent liabilities and establish FTSJ3 as a central regulator of telomere stability in telomerase-active cancers. Targeting FTSJ3 enzymatic activity offers a promising therapeutic entry point, acting upstream of TERRA to eliminate telomerase-driven malignancies selectively.
2026-03-18 | GSE211297 | GEO
Project description:A gene expression signature classifying telomerase and ALT immortalisation reveals an hTERT regulatory network and suggests a mesenchymal stem cell origin for ALT Telomere length is maintained by 2 known mechanisms, activation of telomerase or alternative lengthening of telomeres (ALT). The molecular mechanisms regulating the ALT phenotype are poorly understood and it is unknown how the decision of which pathway to activate is made at the cellular level. We have shown previously that active repression of telomerase gene expression by chromatin remodelling of the promoters is one mechanism of regulation, however other genes and signalling networks are likely to be required to regulate telomerase and maintain the ALT phenotype. Using gene expression profiling we have uncovered a signature of 1305 genes to distinguish telomerase positive and ALT cell lines. By combining this with gene expression profiles of liposarcoma tissue samples we refined this signature to 297 genes significantly associated with telomere maintenance mechanism. Network analysis of known direct interactions between genes within this signature revealed a regulatory signalling network consistent with a model of hTERT repression in ALT cell lines and liposarcomas. This network expands on our existing knowledge of hTERT regulation and provides a platform to understand differential regulation of hTERT in different tumour types and normal tissues. In addition we show evidence to suggest a novel mesenchymal stem cell origin for ALT immortalisation in cell lines and mesenchymal tissues. Keywords: cell type comparison, gene expression
2009-11-02 | GSE14529 | GEO
Project description:A gene expression signature classifying telomerase and ALT immortalisation reveals an hTERT regulatory network and suggests a mesenchymal stem cell origin for ALT Telomere length is maintained by 2 known mechanisms, activation of telomerase or alternative lengthening of telomeres (ALT). The molecular mechanisms regulating the ALT phenotype are poorly understood and it is unknown how the decision of which pathway to activate is made at the cellular level. We have shown previously that active repression of telomerase gene expression by chromatin remodelling of the promoters is one mechanism of regulation, however other genes and signalling networks are likely to be required to regulate telomerase and maintain the ALT phenotype. Using gene expression profiling we have uncovered a signature of 1305 genes to distinguish telomerase positive and ALT cell lines. By combining this with gene expression profiles of liposarcoma tissue samples we refined this signature to 297 genes significantly associated with telomere maintenance mechanism. Network analysis of known direct interactions between genes within this signature revealed a regulatory signalling network consistent with a model of hTERT repression in ALT cell lines and liposarcomas. This network expands on our existing knowledge of hTERT regulation and provides a platform to understand differential regulation of hTERT in different tumour types and normal tissues. In addition we show evidence to suggest a novel mesenchymal stem cell origin for ALT immortalisation in cell lines and mesenchymal tissues. Keywords: cell type comparison, gene expression
2009-11-02 | GSE14487 | GEO
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