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Oncofusion protein AML1-ETO targets ERG factor binding sites in AML

ABSTRACT: ERG has been identified as an essential factor for the function and maintenance of adult hematopoietic stem cells and high ERG expression is a negative prognostic marker for treatment outcome in AML. The molecular function of ERG and its interplay with other factors is however largely unknown. Here we demonstrate that ERG has cell type specific distributions in normal CD34+ myeloid progenitors and in AML cells and identify ERG as a potential pioneering protein for binding of oncofusion protein complexes. In addition, we identify H3 acetylation as the epigenetic mark preferentially associated with ERG binding. This intimate connection between ERG binding and H3 acetylation implies that one of the molecular strategies of the oncofusion proteins PML-RARa and AML1-ETO could involve the targeting of histone deacetylase activities to ETS factor bound hematopoietic regulatory sites.

ORGANISM(S): Homo sapiens

PROVIDER: GSE23730 | GEO | 2012/09/18

SECONDARY ACCESSION(S): PRJNA130783

REPOSITORIES: GEO

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Project description:Epigenetic deregulation plays a critical role in the pathogenesis of Acute Myeloid Leukemia. But changes in histone modification patterns at the epigenome level still remain largely unknown. Here, we analyzed alterations of histone H3 acetylation patterns in a large number of patients with AML compared to CD34+ progenitor cells. Using ChIP-Chip assays, we demonstrate that AML blasts exhibit significant changes in Histone H3 acetylation levels at more than 1000 genomic loci. Importantly, at core promoter regions losses of H3 acetlyation levels prevailed which suggested that a large number of genes is epigenetically silenced in AML. The validation of identified genes led to the discovery of Peroxiredoxin 2 (PRDX2) as a potential tumor suppressor gene in AML. Peroxiredoxin-2 (PRDX2) was silenced in most AML patients by decreased Histone H3 acetylation and in almost 20% by promoter DNA hypermethylation. Low protein expression of the antioxidant PRDX2 gene was clinically associated with a poor prognosis in AML patients. Functionally, PRDX2 acted as an inhibitor of myeloid cell growth by reducing levels of reactive oxygen species generated in response to cytokines. A high level of PRDX2 expression inhibited myc-induced murine leukemogenesis whereas loss of PRDX2 increased myeloid cell proliferation and accelerated myc-induced leukemogenesis. Taken together, we identify widespread loss of Histone H3 acetylation at core promoter regions as a signature of AML blasts. Epigenome wide analyses of histone H3 acetylation led to the identification of PRDX2 as an epigenetically silenced growth suppressor that contributed to the malignant phenotype in AML. Blasts from patients with AML (n=72) were obtained at the time of diagnosis (in a few cases at first relapse). CD34+ progenitor cells (n=17) and white blood cells (n=16) were used as control samples. Immunoprecipitations were performed for anti-acetylated Histone H3. Chromatin-IPs were amplified using ligation mediated PCR and labeled using Cy3 coupled to incorporated amino-allyl-UTP. Common reference DNA consisting of a mixture of genomic DNA from AML patients was prepared, amplified and labeled in a similar way with Cy5.

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Oncofusion protein AML1-ETO targets ERG factor binding sites in AML

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