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Genome-wide co-occupancy of AML1-ETO and N-CoR defines the t(8;21) AML signature in leukemic cells.

ABSTRACT:

Background

Many leukemias result from chromosomal rearrangements. The t(8;21) chromosomal translocation produces AML1-ETO, an oncogenic fusion protein that compromises the function of AML1, a transcription factor critical for myeloid cell differentiation. Because of the pressing need for new therapies in the treatment of acute myleoid leukemia, we investigated the genome-wide occupancy of AML1-ETO in leukemic cells to discover novel regulatory mechanisms involving AML-ETO bound genes.

Results

We report the co-localization of AML1-ETO with the N-CoR co-repressor to be primarily on genomic regions distal to transcriptional start sites (TSSs). These regions exhibit over-representation of the motif for PU.1, a key hematopoietic regulator and member of the ETS family of transcription factors. A significant discovery of our study is that genes co-occupied by AML1-ETO and N-CoR (e.g., TYROBP and LAPTM5) are associated with the leukemic phenotype, as determined by analyses of gene ontology and by the observation that these genes are predominantly up-regulated upon AML1-ETO depletion. In contrast, the AML1-ETO/p300 gene network is less responsive to AML1-ETO depletion and less associated with the differentiation block characteristic of leukemic cells. Furthermore, a substantial fraction of AML1-ETO/p300 co-localization occurs near TSSs in promoter regions associated with transcriptionally active loci.

Conclusions

Our findings establish a novel and dominant t(8;21) AML leukemia signature characterized by occupancy of AML1-ETO/N-CoR at promoter-distal genomic regions enriched in motifs for myeloid differentiation factors, thus providing mechanistic insight into the leukemic phenotype.

SUBMITTER: Trombly DJ

PROVIDER: S-EPMC4434520 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Genome-wide co-occupancy of AML1-ETO and N-CoR defines the t(8;21) AML signature in leukemic cells

Project description:This study characterizes the genome-side occupancy of AML1, AML1-ETO and the cofactors N-CoR and p300 in leukemics cells (Kasumi-1) to discover novel regulatory mechanisms involving genes bound by the t(8:21) fusion protein AML1-ETO. A significant discovery of our study is the co-localization of AML1-ETO with the N-CoR co-repressor on genomic regions that are primarily distal to the transcriptional start sites (TSSs). These regions exhibit over-representation of the PU.1 motif: PU.1 is a key hematopoietic regulator and member of the ETS family of transcription factors. Functionally, genes co-occupied by AML1-ETO and N-CoR (e.g., TYROBP and LAPTM5) are associated with the leukemic phenotype, as determined by analyses of gene ontology and by the observation that these genes are predominantly up-regulated upon AML1-ETO depletion. To further probe the regulatory context of these leukemic cells, genome-wide enrichment of the transcriptional initiation-associated histone modification H3K4me3 was also measured.

2015-05-26 | GSE62847 | GEO

Genome-wide co-occupancy of AML1-ETO and N-CoR defines the t(8;21) AML signature in leukemic cells

2015-05-26 | E-GEOD-62847 | biostudies-arrayexpress

MicroRNA let-7b downregulates AML1-ETO oncogene expression in t(8;21) AML by targeting its 3'UTR.

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Histone deacetylase 3 preferentially binds and collaborates with the transcription factor RUNX1 to repress AML1-ETO-dependent transcription in t(8;21) AML.

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AML1/ETO proteins control POU4F1/BRN3A expression and function in t(8;21) acute myeloid leukemia.

Project description:A variety of genetic lesions, including chromosomal translocations, internal tandem duplications, and mutations, have been described in acute myeloid leukemia (AML). Expression profiling has shown that chromosomal translocations, in particular, are associated with distinctive patterns of gene expression. AML exhibiting the translocation t(8;21), which fuses the AML1 and ETO genes, has such a characteristic expression profile. One gene whose expression is highly correlated with the presence of the AML1/ETO fusion is POU4F1, which encodes the POU homeodomain transcription factor BRN3A. Here we show using specific siRNA in t(8;21) cells and overexpression studies in progenitor cells that AML1/ETO promotes expression of POU4F1/BRN3A. This effect requires DNA-binding function of AML1/ETO, and accordingly, AML1/ETO is bound to the POU4F1 locus in t(8;21) cells. Functionally, whereas overexpression of Brn3a in murine hematopoietic progenitor cells induces terminal myeloid differentiation, coexpression of AML1/ETO or AML1/ETO9a blocks this effect. Furthermore, Brn3a reduction by shRNA impairs AML1/ETO-induced immortalization of murine progenitors. In summary, we identify POU4F1/BRN3A as a novel potential upregulated AML1/ETO target gene whose dramatically high expression may cooperate with AML1/ETO in t(8;21) cells.

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Epigenetic minicircuitry of AML1-ETO/THAP10/MIR383 contributes t(8;21) AML leukemogenesis

Project description:AML1-ETO is regarded as an initial event and plays a pivotal role in t(8;21) acute myeloid leukemia (AML) which is a highly heterogeneous disease. DNA methylation patterns are frequently deregulated in t(8;21) AML, though little is known of the mechanisms through which specific gene sets become aberrantly methylated. Here, We found that the promoter DNA methylation signature of t(8;21) AML blasts differs from those of normal CD34+ bone marrow cells and other AMLs. This signature contains 408 differentially methylated genes, many of which are genes involved in cancer pathway and myeloid leukemia. Database systematic survey and differential methylated regions (DMR) analysis were performed. These study demonstrated that a novel hypermethylated zinc finger containing protein-THAP10 is a target gene and can be epigenetic silenced by AML1-ETO at transcriptional level in t(8;21) AML and silencing of THAP10 by AML1-ETO predicts a poor clinical outcome. Our findings also identified that THAP10 is a bona fide target of miR-383 which can be epigenetic activated by AML1-ETO. In this study, we provided evidence that epigenetic silencing of THAP10 is the mechanistic link between AML1-ETO fusion proteins and tyrosine kinase cascades. In addition, we showed that THAP10 is a nuclear protein which inhibits myeloid proliferation inhibition and promotes differentiation both in vitro and in vivo. Altogether, our results revealed an unexpected and important link between fusion protein AML1-ETO, mir-383, THAP10 and tyrosine cascades in t(8;21) AML.

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AML1/ETO oncoprotein is directed to AML1 binding regions and co-localizes with AML1 and HEB on its targets.

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The RUNX1-ETO target gene RASSF2 suppresses t(8;21) AML development and regulates Rac GTPase signaling.

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