The t(8;21) fusion product, AML-1-ETO, associates with C/EBP-alpha, inhibits C/EBP-alpha-dependent transcription, and blocks granulocytic differentiation

Mol Cell Biol. 1998 Jan;18(1):322-33. doi: 10.1128/mcb.18.1.322.

Abstract

AML-1B is a hematopoietic transcription factor that is functionally inactivated by multiple chromosomal translocations in human acute myeloblastic and B-cell lymphocytic leukemias. The t(8;21)(q22;q22) translocation replaces the C terminus, including the transactivation domain of AML-1B, with ETO, a nuclear protein of unknown function. We previously showed that AML-1-ETO is a dominant inhibitor of AML-1B-dependent transcriptional activation. Here we demonstrate that AML-1-ETO also inhibits C/EBP-alpha-dependent activation of the myeloid cell-specific, rat defensin NP-3 promoter. AML-1B bound the core enhancer motifs present in the NP-3 promoter and activated transcription approximately sixfold. Similarly, C/EBP-alpha bound NP-3 promoter sequences and activated transcription approximately sixfold. Coexpression of C/EBP-alpha with AML-1B or its family members, AML-2 and murine AML-3, synergistically activated the NP-3 promoter up to 60-fold. The t(8;21) product, AML-1-ETO, repressed AML-1B-dependent activation of NP-3 and completely inhibited C/EBP-alpha-dependent activity as well as the synergistic activation. In contrast, the inv(16) product, which indirectly targets AML family members by fusing their heterodimeric DNA binding partner, CBF-beta, to the myosin heavy chain, inhibited AML-1B but not C/EBP-alpha activation or the synergistic activation. AML-1-ETO and C/EBP-alpha were coimmunoprecipitated and thus physically interact in vivo. Deletion mutants demonstrated that the C terminus of ETO was required for AML-1-ETO-mediated repression of the synergistic activation but not for association with C/EBP-alpha. Finally, overexpression of AML-1-ETO in myeloid progenitor cells prevented granulocyte colony-stimulating factor-induced differentiation. Thus, AML-1-ETO may contribute to leukemogenesis by specifically inhibiting C/EBP-alpha- and AML-1B-dependent activation of myeloid promoters and blocking differentiation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • CCAAT-Enhancer-Binding Proteins
  • COS Cells
  • Cell Differentiation / genetics
  • Chromosomes, Human, Pair 21*
  • Chromosomes, Human, Pair 8*
  • Core Binding Factor Alpha 2 Subunit
  • DNA-Binding Proteins / genetics*
  • Gene Expression Regulation, Neoplastic
  • Granulocytes / cytology
  • Granulocytes / metabolism*
  • Hematopoiesis / genetics
  • Humans
  • Leukemia / genetics
  • Nuclear Proteins / genetics*
  • Oncogene Proteins, Fusion*
  • Promoter Regions, Genetic / genetics
  • RUNX1 Translocation Partner 1 Protein
  • Rats
  • Recombinant Fusion Proteins / genetics
  • Transcription Factors / genetics*
  • Transcription, Genetic*
  • Translocation, Genetic*

Substances

  • AML1-ETO fusion protein, human
  • CCAAT-Enhancer-Binding Proteins
  • Core Binding Factor Alpha 2 Subunit
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Oncogene Proteins, Fusion
  • RUNX1 Translocation Partner 1 Protein
  • Recombinant Fusion Proteins
  • Transcription Factors