Gene expression and ChIP-chip analysis of U251 human glioblastoma cell line
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
SUBMITTER: Quante T
PROVIDER: S-ECPF-GEOD-35500 | biostudies-other | 2012 Sep
REPOSITORIES: biostudies-other
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Project description:The human TP53 gene is frequently mutated in tumors and cell lines. Unlike other tumor suppressors that are commonly inactivated by deletions or nonsense mutations, the majority of p53-mutations are missense point mutations that result in the expression of a full-length protein with an altered amino acid that has lost sequence specific DNA-binding. Expression of mutant p53 (mutp53) confers advantages to tumor cells and transcriptional regulation of several genes mediating the beneficial effects has been shown to play a role. However, molecular mechanisms of transcriptional regulation by mutp53 are still poorly understood. We used the glioblastoma-derived U-251 MG human cell line endogenously expressing mutp53 protein (R273H mutation) to analyze gene expression profiles on Agilent Whole Human Genome Microarray after transient and stable depletion of mutp53 expression. Gene expression data was correlated with a ChIP study on a custom tiling array to understand the contribution of endogenously expressed mutp53 to transcriptional regulation. This series of microarray experiments contains the gene expression profiles of glioblastoma-derived U-251 MG human cell lines engineered to constitutively express a p53-specific shRNA or scrambled control shRNA. To reverse the effect of mutp53 depletion, stable clones were modified by stable integration of a mutp53-R273H expression construct or empty pCDNA3 vector as a control. In addition, we performed gene expression analysis of U-251 MG cells transiently transfected with p53-specific siRNA or control siRNA (3 biological replicates each).
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Project description:Using human U251 glioblastoma cells with endogenous mutp53 expression as a model, we performed a ChIP-chip analysis of mutp53 binding sites on a custom tiling array, coupled with global expression profiling and an analysis of the epigenetic status of mutp53 regulated promoters. Mutp53 binds preferentially, and independent of other transcription factors (e.g. ETS1 and SP1), to G/C-rich DNA stretches around transcriptional start sites (TSS) of many genes. Mutp53-bound regions are frequently located in CpG islands and are highly prone to adopt non-B DNA conformation(s). Analysis of the transcriptional status of mutp53-regulated genes demonstrated that mutp53 generally modulates transcription from active promoters marked by H3K4me3. Based on our data we propose a dual mode model of mutp53 GOF, which includes both stochastic and deterministic components. On a local scale, mutp53 acts as a basal transcriptional co-factor that has the potential to bind autonomously and selectively to non-B DNA structures around TSSs of active genes and to modulate transcription rates of many genes in a context and stimulus-dependent fashion. Resulting stochastic alterations generate transcriptional plasticity and enhance transcriptional competence on a global scale. This SuperSeries is composed of the SubSeries listed below. Refer to individual Series
2012-12-10 | E-GEOD-35500 | biostudies-arrayexpress
Project description:Using human U251 glioblastoma cells with endogenous mutp53 expression as a model, we performed a ChIP-chip analysis of mutp53 binding sites on a custom tiling array, coupled with global expression profiling and an analysis of the epigenetic status of mutp53 regulated promoters. Mutp53 binds preferentially, and independent of other transcription factors (e.g. ETS1 and SP1), to G/C-rich DNA stretches around transcriptional start sites (TSS) of many genes. Mutp53-bound regions are frequently located in CpG islands and are highly prone to adopt non-B DNA conformation(s). Analysis of the transcriptional status of mutp53-regulated genes demonstrated that mutp53 generally modulates transcription from active promoters marked by H3K4me3. Based on our data we propose a dual mode model of mutp53 GOF, which includes both stochastic and deterministic components. On a local scale, mutp53 acts as a basal transcriptional co-factor that has the potential to bind autonomously and selectively to non-B DNA structures around TSSs of active genes and to modulate transcription rates of many genes in a context and stimulus-dependent fashion. Resulting stochastic alterations generate transcriptional plasticity and enhance transcriptional competence on a global scale. This SuperSeries is composed of the SubSeries listed below.
2012-12-10 | GSE35500 | GEO
Project description:The human TP53 gene is frequently mutated in tumors and cell lines. Unlike other tumor suppressors that are commonly inactivated by deletions or nonsense mutations, the majority of p53-mutations are missense point mutations that result in the expression of a full-length protein with an altered amino acid that has lost sequence specific DNA-binding. Expression of mutant p53 (mutp53) confers advantages to tumor cells and transcriptional regulation of several genes mediating the beneficial effects has been shown to play a role. However, molecular mechanisms of transcriptional regulation by mutp53 are still poorly understood. We used the glioblastoma-derived U-251 MG human cell line endogenously expressing mutp53 protein (R273H mutation) to analyze gene expression profiles on Agilent Whole Human Genome Microarray after transient and stable depletion of mutp53 expression. Gene expression data was correlated with a ChIP study on a custom tiling array to understand the contribution of endogenously expressed mutp53 to transcriptional regulation.
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Project description:The human TP53 gene is frequently mutated in tumors and cell lines. Unlike other tumor suppressors that are commonly inactivated by deletions or nonsense mutations, the majority of p53-mutations are missense point mutations that result in the expression of a full-length protein with an altered amino acid that has lost sequence specific DNA-binding. Expression of mutant p53 (mutp53) confers advantages to tumor cells and transcriptional regulation of several genes mediating the beneficial effects has been shown to play a role. However, molecular mechanisms of transcriptional regulation by mutp53 are still poorly understood. We used the glioblastoma-derived U-251 MG human cell line endogenously expressing mutp53 protein (R273H mutation) to analyze gene expression profiles on Agilent Whole Human Genome Microarray after transient and stable depletion of mutp53 expression. Gene expression data was correlated with a ChIP study on a custom tiling array to understand the contribution of endogenously expressed mutp53 to transcriptional regulation. This series of microarray experiments contains the gene expression profiles of glioblastoma-derived U-251 MG human cell lines engineered to constitutively express a p53-specific shRNA or scrambled control shRNA. To reverse the effect of mutp53 depletion, stable clones were modified by stable integration of a mutp53-R273H expression construct or empty pCDNA3 vector as a control. In addition, we performed gene expression analysis of U-251 MG cells transiently transfected with p53-specific siRNA or control siRNA (3 biological replicates each).
2012-12-10 | E-GEOD-35454 | biostudies-arrayexpress
Project description:Musashi1 (Msi1) is a highly conserved RNA binding protein that is required during the development of the nervous system. Msi1 has a role in neural stem cells, controlling the balance between self-renewal and differentiation. Msi1 has also been implicated in cancer, being highly expressed in multiple tumor types. In this study, we analyzed Msi1 expression in a large cohort of medulloblastoma samples and showed that Msi1 is highly expressed in tumor tissue compared to normal cerebellum and that high Msi1 expression is associated with a poor prognosis. Using a nude mouse xenograft model, we demonstrate that Msi1 is important for tumor growth. We then used RIP-chip (ribonucleoprotein immunoprecipitation followed by microarray analysis) to identify mRNA targets of Msi1 in medulloblastoma. In conclusion, our results suggest that Msi1 functions as a regulator of multiple processes in medulloblastoma formation and could become an important therapeutic target. RIP-Chip analysis to identify mRNA preferentially associated with Msi1 protein. RIP-Chip experiments were performed on two biologically replicated samples. A total of 8 microarrays were carried on using technical replicates of Msi1 antibody vs. prebleed serum for each dye orientation. We prepared two biological replicates for two different arrays. Each array consisted of 4 microarrays with 2 replicates for each dye orientation.
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Project description:Missense mutations in the TP53 gene are frequent genetic alterations in human tumor tissue and cell lines. In contrast to wild-type p53, the mutant p53 (mutp53) protein has lost the transcriptional activity towards pro-apoptotic and growth arrest genes, but retained the property to interact with DNA in a structure-specific fashion. Expression of mutp53 is advantageous for tumor cells, however the molecular mechanism of mutp53 action is still not known. We used the glioblastoma-derived U-251 MG human cell line to analyze DNA binding of mutant p53 (R273H mutation) on a Nimblegen custom 135k tiling array and to correlate mutp53 binding regions with the epigenetic state and occupation by other transcription factors (ETS1 and SP1). We found that mutp53-binding regions are G/C-rich and are located around transcriptional start sites (TSS) of many protein-coding genes, which in most cases are active, but are not always regulated upon transient mutp53 depletion. We propose a model which does not only rely on interactions of mutp53 with diverse transcriptional regulators at active promoters, but primarily is based on a DNA binding activity of mutp53. We designed a Nimblegen custom 135k tiling array that covers a large set of putative and known p53 (wild-type and mutant) target genes in the human genome. For analysis of the epigenetic state of genes covered by the tiling array in control and mutant p53-depleted U251 cells we focused on changes in active histone marks, H3K4me3 and H3K9Ac, and RNA polymerase II recruitment and processivity. H3K4me3 and H3K9Ac marks are enriched in active promoter regions and the phosphorylation of serine 5 (S5-P) and serine 2 (S2-P) in the CTD of RNA polymerase II have been described to define initiated and elongating complexes, respectively. We performed the ChIP-chip experiments for H3K4me3, H3K9Ac, RNA polymerase II (S5-P) and RNA polymerase II (S2-P) from U251 cells transfected with p53-specific siRNA or control siRNA (2 biological replicates each). To analyze binding of mutant p53 to the genes covered by the tiling array we performed mutant p53 ChIP-chip experiments in 4 biological replicates of. In addition, we analyzed the distribution of SP1 and ETS1 binding sites in 3 biological replicates.
2012-12-10 | E-GEOD-35453 | biostudies-arrayexpress
Project description:Missense mutations in the TP53 gene are frequent genetic alterations in human tumor tissue and cell lines. In contrast to wild-type p53, the mutant p53 (mutp53) protein has lost the transcriptional activity towards pro-apoptotic and growth arrest genes, but retained the property to interact with DNA in a structure-specific fashion. Expression of mutp53 is advantageous for tumor cells, however the molecular mechanism of mutp53 action is still not known. We used the glioblastoma-derived U-251 MG human cell line to analyze DNA binding of mutant p53 (R273H mutation) on a Nimblegen custom 135k tiling array and to correlate mutp53 binding regions with the epigenetic state and occupation by other transcription factors (ETS1 and SP1). We found that mutp53-binding regions are G/C-rich and are located around transcriptional start sites (TSS) of many protein-coding genes, which in most cases are active, but are not always regulated upon transient mutp53 depletion. We propose a model which does not only rely on interactions of mutp53 with diverse transcriptional regulators at active promoters, but primarily is based on a DNA binding activity of mutp53.
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