Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Activation and repression by oncogenic Myc shapes tumour-specific gene expression profiles

ABSTRACT: In mammalian cells, the Myc oncoprotein binds to thousands of promoters. During mitogenic stimulation of primary lymphocytes, Myc promotes an increase in expression of virtually all genes. In contrast, Myc-driven tumour cells differ from normal cells in expression of specific sets of up- and downregulated genes that have significant prognostic value. To understand this discrepancy, we studied the consequences of inducible expression and depletion of Myc in human cells and murine tumour models. Changes in Myc levels activate and repress specific sets of direct target genes that are characteristic of Myc-transformed tumour cells. Three factors account for this specificity: First, the magnitude of response parallels the change in occupancy by Myc at each promoter. Functionally distinct classes of target genes differ in the E-box sequence bound by Myc, arguing that different cellular responses to physiological and oncogenic Myc levels are controlled by promoter affinity. Secondly, Myc both positively and negatively affects transcription initiation independent of its effect on transcriptional elongation. Third, complex formation with Miz1 mediates repression of multiple target genes by Myc and the ratio of Myc and Miz1 bound to each promoter correlates with the direction of response. Myc, Miz1 and RNA polymerase II ChIPseq as well as RNAseq experiments in two human cancer cell lines and murine carcinoma cells as well as fibroblasts from Miz1M-bM-^HM-^FPOZ mice. All sequencing experiment were performed on an Illumina Genome Analyzer IIx.

ORGANISM(S): Homo sapiens

SUBMITTER: Susanne Walz

PROVIDER: E-GEOD-44672 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Activation and repression by oncogenic MYC shape tumour-specific gene expression profiles.

Walz Susanne S Lorenzin Francesca F Morton Jennifer J Wiese Katrin E KE von Eyss Björn B Herold Steffi S Rycak Lukas L Dumay-Odelot Hélène H Karim Saadia S Bartkuhn Marek M Roels Frederik F Wüstefeld Torsten T Fischer Matthias M Teichmann Martin M Zender Lars L Wei Chia-Lin CL Sansom Owen O Wolf Elmar E Eilers Martin M

Nature 20140709 7510

In mammalian cells, the MYC oncoprotein binds to thousands of promoters. During mitogenic stimulation of primary lymphocytes, MYC promotes an increase in the expression of virtually all genes. In contrast, MYC-driven tumour cells differ from normal cells in the expression of specific sets of up- and downregulated genes that have considerable prognostic value. To understand this discrepancy, we studied the consequences of inducible expression and depletion of MYC in human cells and murine tumour ...[more]

PMID: 25043018

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Project description:Medulloblastoma (MB) is the most common malignant brain tumor. MB is a cerebellar tumor that occurs mostly in children between the ages of 3-7 years but also in adults. Human MBs are classified into four subgroups: Wingless (WNT), Sonic Hedgehog (SHH), Group 3 (G3) and G4, each of which with distinct molecular signatures. SHH MBs with MYCN amplification and TP53 mutations and G3 MBs characterized by C-MYC (MYC) overexpression in ~17% of cases from gene amplification with stem like properties, are the most aggressive and least curable with current therapeutic regimen. Using an orthotopic transplant approach, we found that enforced expression of MYCN in cerebellar granule neural progenitors (CGNPs) from 5-7 days old Trp53-null mice induced SHH MBs after transfer in the cortices or cerebella of naive recipient mice. In contrast, overexpression of MYC induced G3 MBs. Because MYCN and MYC bind to the same E-box DNA sequences, we hypothesized that the difference between MYC and MYCN-induced gene expression and tumor identity might be due to their interaction with different partners in CGNPs. In this study, we investigated the role of the Myc interacting zinc finger protein 1 (MIZ1). We found that MIZ1 binds with higher affinity to MYC than to MYCN and that MIZ1 and MYC co-occupy thousands of promoters in G3 MB. Remarkably, enforced expression of a MYC mutant (MYCV394D) that no longer binds to MIZ1 in Trp53-null CGNPs or expression of wild type MYC in CGNPs that lack functional Miz1 resulted in massive changes of the resulting tumorâ??s transcriptional program. Tumors differed from both SHH and G3 medulloblastoma and had a later time of onset compared to MYC-driven G3 medulloblastoma. Our data demonstrate that interaction of MYC with MIZ1 is required for the development of G3 medulloblastoma. ChIP-Seq experiments for Miz1, c-Myc and NMyc from murine medulloblastoma material. Either sorted tumor cells (Miz1 and c-Myc) or spheres from tumor cells (Miz1 and NMyc) were used. Input-samples were sequenced as controls. RNA-Seq from G3 medulloblastomas after restoration of Atoh1 expression.

Dataset Information

Activation and repression by oncogenic Myc shapes tumour-specific gene expression profiles

Publications

Activation and repression by oncogenic MYC shape tumour-specific gene expression profiles.

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