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Transcription poisoning by topoisomerase I is controlled by gene length, splice sites and miR-142-3p

ABSTRACT: DNA topoisomerase I (Top1) is required for transcription as it relaxes positive and negative supercoils by forming transient Top1 cleavage complexes (Top1cc) up- and down-stream of transcription complexes. However, Top1cc can also be trapped by endogenous DNA lesions and by camptothecin (CPT) and its anticancer derivatives, which results in transcription blocks. Here, we undertook a genome-wide analysis of the effects of CPT on gene expression at exon resolution. We tested the impact of Top1 inhibition on gene expression at the genome-wide level in human colon carcinoma HCT116 and human breast carcinoma MCF7 cells. The RNA of cells treated with camptothecin (CPT) for various times was analyzed with Affy Exon array (GeneChip Human Exon 1.0 ST array). Moreover, we tested the impact of Top1 down-regulation on gene expression at the genome-wide level in human colon carcinoma HCT116 cells. The RNA of cells treated transfected with a Top1 siRNA was analyzed with Affy Exon array (GeneChip Human Exon 1.0 ST array).

ORGANISM(S): Homo sapiens

SUBMITTER: Michael Ryan

PROVIDER: E-GEOD-37352 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Topoisomerase I cleavage complexes preferentially down-regulate ubiquitin- and RNA degradation-related transcripts in relationship to gene length, exon-intron junctions and p53-dependent up-regulation of miR-142-3p [miRNA]

Project description:DNA topoisomerase I (Top1) is required for transcription as it relaxes positive and negative supercoils by forming transient Top1 cleavage complexes (Top1cc) up- and down-stream of transcription complexes. However, Top1cc can also be trapped by endogenous DNA lesions and by camptothecin (CPT) and its anticancer derivatives, which results in transcription blocks. Here, we undertook a genome-wide analysis of the effects of CPT on gene expression at exon resolution. We tested the impact of Top1 inhibition on miRNA expression at the genome-wide level in human colon carcinoma HCT116. The miRNA of cells treated with camptothecin (CPT) for were measured at several timepoints with Agilent Human miRNA Microarray V3 (8x15K).

2013-04-17 | E-GEOD-37357 | biostudies-arrayexpress

siRNA profiling of stable HCT116-siTop1 and MCF-7-siTop1 cell lines reveal non-classical functions of human Topoisomerase I:

Project description:The biological functions of nuclear topoisomerase I (Top1) have been difficult to study because knocking out TOP1 is lethal in metazoans. To reveal the functions of human Top1, we have generated stable Top1siRNA cell lines from colon and breast carcinomas (HCT116-siTop1 and MCF-7-siTop1, respectively). In those cells, Top2 compensates for Top1 deficiency. A prominent feature of the siTop1 cells is genomic instability, with chromosomal aberrations and histone gamma-H2AX foci associated with replication. siTop1 cells also show rDNA and nucleolar alterations, and increased nuclear volume. Genome-wide transcription profiling revealed 55 genes with consistent changes in siTop1 cells. Among them, asparagine synthetase (ASNS) was reduced in siTop1 cells, as it also was in cells with transient Top1 downregulation. Conversely, Top1 complementation increased ASNS, indicating a causal link between Top1 and ASNS expression. Correspondingly, pharmacological profiling showed l-asparaginase hypersensitivity in the siTop1 cells. Resistance to camptothecin, aphidicolin, hydroxyurea and staurosporine, and hypersensitivity to etoposide and actinomycin D demonstrated that Top1, in addition to being the target of camptothecins, also regulates DNA replication, rDNA stability and apoptosis. Overall, our studies demonstrate the pleiotropic nature of human Top1 activities. In addition to its classical DNA nicking-closing functions, Top1 plays critical non-classical roles in genomic stability, gene-specific transcription, and response to various anticancer agents. Experiment Overall Design: We are using Affymetrix whole genome array U133 Plus 2, which is a single color microarray platform. For colon experiments, we analyzed 2 different samples as 4 replicates. For breast experiments, we analyzed 2 samples as replicates.

2008-06-15 | E-GEOD-7161 | biostudies-arrayexpress

Genome-wide analysis of novel splice variants induced by topoisomerase I poisoning shows preferential occurrence in genes encoding splicing factors

Project description:Topoisomerase I (Top1) relaxes both positive and negative supercoilings by producing transient Top1 cleavage complexes (Top1cc). Several studies have suggested the implication of Top1 in splicing. Here, we tested the implication of Top1cc in splicing at the global genome level in human carcinoma cells to determine whether Top1 inhibition selectively affects particular families of genes. We tested the impact of Top1 inhibition on splicing at the genome-wide level in human colon carcinoma HCT116 cells. The RNA of HCT116 cells treated with camptothecin (CPT) for various times was analyzed with ExonHit Human Splice Array.

2011-07-21 | E-GEOD-23677 | biostudies-arrayexpress

Project description:This SuperSeries is composed of the SubSeries listed below. Refer to individual Series

2013-04-17 | E-GEOD-37358 | biostudies-arrayexpress

Genome-Wide Transcriptional Effects of the Anti-Cancer Agent Camptothecin

Project description:The anti-cancer drug camptothecin inhibits replication and transcription by trapping DNA topoisomerase I (Top1) covalently to DNA in a M-bM-^@M-^\cleavable complexM-bM-^@M-^]. To examine the effects of camptothecin on RNA synthesis genome-wide we used Bru-Seq and show that camptothecin treatment affected transcription initiation, elongation, termination, splicing and enhancer activity. Following removal of camptothecin, transcription spread as a wave from the 5M-bM-^@M-^Y-end of genes with no recovery of transcription apparent from RNA polymerases stalled in the body of genes. As a result, camptothecin preferentially inhibited the expression of large genes such as proto-oncogenes, and anti-apoptotic genes while smaller ribosomal protein genes, pro-apoptotic genes and p53 target genes showed relative higher expression. In addition, a set of mitotic regulator genes and histone genes were inhibited in a size-independent manner. Cockayne syndrome group B fibroblasts showed a very similar RNA synthesis recovery profile to normal fibroblasts suggesting that transcription-coupled repair is not involved in the repair of transcription-blocking TOP1 lesions. These findings of the effects of camptothecin on transcription have important implications for its anti-cancer activities and may aid in the design of improved combinatorial treatments involving Top1 poisons. Analysis of the effect of Camptothecin (CPT) on transcription. Normal fibroblasts and Cockayne syndrome group B fibroblasts were exposed to CPT for 60 minutes, after which a washout was performed. Nascent RNA was labeled using bromouridine for 15 minutes starting at time points: 1) 15 minutes before the washout; 2) Immediately after the washout; 3) 15 minutes after the washout. Test samples are compared to control cells that were not exposed to CPT.

2013-10-29 | E-GEOD-48678 | biostudies-arrayexpress

Camptothecin-miRNA

Project description:DNA Topoisomerase I inhibition by Camptothecin (CPT) derivatives can impair the hypoxia-induced cell transcriptional response. In the present work, we determined molecular aspects of the mechanism of CPT effects on HIF-1alpha activity in human cancer cells. In particular, we provide evidence that low concentrations of CPT, without interfering with HIF-1alpha mRNA levels, can reduce HIF-1alpha protein expression and activity. As luciferase assays demonstrated the involvement of the HIF-1alpha mRNA 3M-^RUTR in CPT-induced impairment of HIF-1alpha protein regulation, we performed microarray analysis to identify CPT-induced modification of miRNAs targeting HIF-1alpha mRNA under hypoxic-mimetic conditions. The selected miRNAs were then further analyzed demonstrating a role for miR-17-5p and miR-155 in HIF-1alpha protein expression after CPT treatments. The present findings establish miRNAs as key factors in a molecular pathway connecting Top1 inhibition and human HIF-1alpha protein regulation and activity, widening the biological and molecular activity of CPT derivatives and the perspective for novel clinical interventions.

2013-12-02 | E-MTAB-2022 | biostudies-arrayexpress

2013-04-17 | GSE37357 | GEO

Transcription poisoning by topoisomerase I is controlled by gene length, splice sites and miR-142-3p

2013-04-17 | GSE37352 | GEO

Snd1-Mtdh interaction regulates cell survival under camptothecin-induced replication stress

Project description:PyMT tumor cells with indicated status of Mtdh and Snd1 were treated with camptothecin (CPT) and the transcirptome profiles were determined and compared two sets of experiments: (1) vector control vs Snd1-KD under CPT treament (2) PyMT/Mtdh-KO cells reconstituted with either WT or Snd1-binding deficient mutant Mtdh (W391D) under CPT treatment

2014-08-12 | E-GEOD-55522 | biostudies-arrayexpress

Expression data from camptothecin-treated rat primary motor neurons

Project description:Topoisomerase 1 (TOP1) poisons like camptothecin (CPT), which are used as chemotherapeutic agents in cancer, elicit DNA damage in quiescient neurons. In this study, we examined the effects of CPT and actinomycin D (ActD) on neuronal cells. Motor (MNs) and cortical (CNs) neurons were more susceptible to the toxic effects of CPT and ActD than fibroblasts. MNs and CNs exhibited a delayed DNA damage response—increase in nuclear γ-H2AX foci—relative to fibroblasts. Neuronal cells expressed higher levels of Top1 mRNA than fibroblasts which could explain their enhanced vulnerability to CPT and ActD toxicity. Microarray analysis was performed to identify differentially regulated transcripts in MNs treated with CPT for 2 hours. Many immediate-early genes including Fos and Egr-1 were upregulated in CPT-treated MNs. Fos mRNA levels were elevated in all cells types treated with CPT; Egr-1 transcript levels, however, were reduced in CPT-treated fibroblasts even though they were elevated in treated MNs and CNs. Pathway and network analysis of the differentially expressed transcripts revealed activation of ERK and JNK signaling cascades in CPT-treated MNs. In conclusion, MNs were more vulnerable than fibroblasts to the damaging effects of TOP1 poisons and they elicit a unique intracellular response to CPT treatment.

2016-09-20 | GSE67146 | GEO

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