AML1/Runx1 Recruits Calcineurin to Regulate Granulocyte Macrophage Colony-stimulating Factor by Ets1 Activation

Abstract

Acute myeloid leukemia 1 (AML1), also denoted Runx1, is a transcription factor essential for hematopoiesis, and the AML1 gene is the most common target of chromosomal translocations in human leukemias. AML1 binds to sequences present in the regulatory regions of a number of hematopoiesis-specific genes, including certain cytokines such as granulocyte macrophage colony-stimulating factor (GM-CSF) up-regulated after T cell receptor stimulation. Here we show that both subunits of the Ca 2؉ / calmodulin-dependent protein phosphatase calcineurin (CN), which is activated upon T cell receptor stimulation, interact directly with the N-terminal runt homology domain-containing part of AML1. The regulatory CN subunit binds AML1 with a higher affinity and in addition also interacts with the isolated runt homology domain. The related Runx2 transcription factor, which is essential for bone formation, also interacts with CN. A constitutively active derivative of CN is shown to activate synergistically the GM-CSF promoter/enhancer together with AML1 or Runx2. We also provide evidence that relief of the negative effect of the AML1 sites is important for Ca 2؉ activation of the GM-CSF promoter/enhancer and that AML1 overexpression increases this Ca 2؉ activation. Both subunits of CN interact with AML1 in coimmunoprecipitation analyses, and confocal microscopy analysis of cells expressing fluorescence-tagged protein derivatives shows that CN can be recruited to the nucleus by AML1 in vivo. Mutant analysis of the GM-CSF promoter shows that the Ets1 binding site of the promoter is essential for the synergy between AML1 and CN in Jurkat T cells. Analysis of the effects of inhibitors of the protein kinase glycogen synthase kinase-3␤ and in vitro phosphorylation/dephosphorylation analysis of Ets1 suggest that glycogen synthase kinase-3␤-phosphorylated Ets1 is a target of AML1-recruited CN phosphatase at the GM-CSF promoter.

IFN-γ-mediated hematopoietic cell destruction in murine models of immune-mediated bone marrow failure

“…As a key member of the Ets family of transcription factors, Ets-1 is a positive regulator of hematopoietic differentiation and lineage specification. [56][57][58][59][60][61] Therefore, the effect of IFN-g-mediated Ets-1 downregulation is consistent with IFN-g as a negative regulator, acting directly on murine HSCs.…”

Thymomegaly, Microsplenia, and Defective Homeostatic Proliferation of Peripheral Lymphocytes in p51-Ets1 Isoform-Specific Null Mice

“…Collectively, these distinctions contribute to the Ets1 isoform-specific modulation of particular Ets1 target genes. Exon VII-mediated homotypic and AML1 (Runx1)-Ets1 heterotypic protein-protein interactions augment transcription of MMP-3 and granulocyte-macrophage colony-stimulating factor, respectively (2,35,36). Conversely, other target genes, such as the VE-cadherin gene, are transcriptionally activated more strongly by the p42-Ets1 variant in a cell context-specific manner (33).…”

A T Lymphocyte-Specific Transcription Complex Containing RUNX1 Activates MHC Class I Expression

“…RUNX1 expression is limited to hemopoietic tissues and is considered a master regulator of hematopoiesis (44 -46). In addition to the TCR genes, RUNX1 regulates a number of genes involved in cell cycle and hemopoietic development, including the cytokine genes IL-3 (47), MIP-1␣ (48,49), and GM-CSF (CSF2) (50), the macrophage CSF receptor (51, Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 52), and the tumor suppressor genes p21 WAF-1 (53) and p14 ARF (54). RUNX1 acts as both a transcriptional activator and repressor: RUNX1 represses CD4 gene expression by binding a silencer element in the CD4 locus (55,56).…”