Differential involvement of E2A-corepressor interactions in distinct leukemogenic pathways

Abstract

E2A is a member of the E-protein family of transcription factors. Previous studies have reported context-dependent regulation of E2A-dependent transcription. For example, whereas the E2A portion of the E2A-Pbx1 leukemia fusion protein mediates robust transcriptional activation in t(1;19) acute lymphoblastic leukemia, the transcriptional activity of wild-type E2A is silenced by high levels of corepressors, such as the AML1-ETO fusion protein in t(8;21) acute myeloid leukemia and ETO-2 in hematopoietic cells. Here, we show that, unlike the HEB E-protein, the activation domain 1 (AD1) of E2A has specifically reduced corepressor interaction due to E2A-specific amino acid changes in the p300/CBP and ETO target motif. Replacing E2A-AD1 with HEB-AD1 abolished the ability of E2A-Pbx1 to activate target genes and to induce cell transformation. On the other hand, the weak E2A-AD1-corepressor interaction imposes a critical importance on another ETO-interacting domain, downstream ETO-interacting sequence (DES), for corepressor-mediated repression. Deletion of DES abrogates silencing of E2A activity by AML1-ETO in t(8;21) leukemia cells or by ETO-2 in normal hematopoietic cells. Our results reveal an E2A-specific mechanism important for its context-dependent activation and repression function, and provide the first evidence for the differential involvement of E2A-corepressor interactions in distinct leukemogenic pathways.

E2a Is Necessary for Smad2/3-Dependent Transcription and the Direct Repression of lefty during Gastrulation

“…In the absence of E2a, many genes (3000+) are upregulated, suggesting that E2a acts broadly as a transcriptional repressor, and many genes gain Smad2/3 binding (571) or have shifted Smad2/3 binding (192). At some loci, E2a may also act more directly as a repressor by recruiting corepressors, as does in association with ETO/MTG corepressors in hematopoiesis (Gow et al, 2014; Guo et al, 2009; Zhang et al, 2004). However, Lefty is by far the most critical target of E2a repression for early cell fate specification, as downregulation of Lefty is sufficient to rescue expression of mesoderm genes in E2a depleted embryos.…”

“…In B cell development, E2a can act as either a transcriptional activator or repressor through its association with coactivators and corepressors or by forming homodimers and heterodimer in association with other class I or class II bHLH proteins, which can be repressors or activators (reviewed in (Kee, 2009)). E2a can also associate with transcriptional coactivators such as p300, CBP and TAF4 through one of two AD transactivation domains (Bayly et al, 2004; Bradney et al, 2003; Chen et al, 2013), or with the ETO/MTG class of corepressors through the AD2 and DES domains (Gow et al, 2014; Guo et al, 2009; Zhang et al, 2004). E2a can therefore have potentially widespread effects on transcriptional regulation across the genome, although the effects of E2a loss of function on global transcription patterns have not been investigated.…”

The Optimal Corepressor Function of Nuclear Receptor Corepressor (NCoR) for Peroxisome Proliferator-activated Receptor γ Requires G Protein Pathway Suppressor 2

“…Quantitative RT-PCR (RT-qPCR) and RNA Sequencing (RNASeq)-RT-qPCR experiments were performed as described previously (39). The primers used in this study are shown below.…”

Enforced expression of E47 has differential effects on Lmo2-induced T-cell leukemias

“…Since it can bind E2A proteins and Heb, it could perturb the balance of these proteins either in macromolecular complexes or as homo- or heterodimers, which may ultimately affect the transcription of targets. Mtg16 is a relatively weak interactor with E47 compared with Heb and it appears to be dispensable for the development of Lmo2-induced T-cell leukemia since it is absent in the 080 line (50). Even so, it is required for normal T-cell development and it is part of the Lmo2-associated complex in erythroid progenitor cells (51).…”