Unknown,Transcriptomics,Genomics,Proteomics

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Miz1 is required to maintain autophagic flux

ABSTRACT: Miz1 is a zinc finger protein that regulates expression of cell cycle inhibitors as part of a complex with Myc. Cell cycle-independent functions of Miz1 are poorly understood. Here, we use a Nestin-Cre transgene to delete an essential domain of Miz1 in the central nervous system (Miz1M-NM-^TPOZNes). Miz1M-NM-^TPOZNes mice display cerebellar neurodegeneration characterized by the progressive loss of Purkinje cells. Chromatin immunoprecipitation sequencing and biochemical analyses show that Miz1 activates transcription upon binding to a non-palindromic sequence present in core promoters. Target genes of Miz1 encode regulators of autophagy and proteins involved in vesicular transport that are required for autophagy. Miz1M-NM-^TPOZ neuronal progenitors and fibroblasts show reduced autophagic flux. Consistently, polyubiquitinated proteins and p62/Sqtm1 accumulate in the cerebella of Miz1M-NM-^TPOZNes mice, characteristic features of defective autophagy. Our data suggest that Miz1 may link cell growth and ribosome biogenesis to the transcriptional regulation of vesicular transport and autophagy. ChIP-Seq with H190 and G18 on an Illumina Genome Analyzer IIx.

ORGANISM(S): Homo sapiens

SUBMITTER: Sven Griep

PROVIDER: E-GEOD-48602 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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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.

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Miz1 is required to maintain autophagic flux

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