Functional redundancy between the transcriptional activation domains of E2A is mediated by binding to the KIX domain of CBP/p300

Abstract

The E-protein transcription factors play essential roles in lymphopoiesis, with E12 and E47 (hereafter called E2A) being particularly important in B cell specification and maturation. The E2A gene is also involved in a chromosomal translocation that results in the leukemogenic oncoprotein E2A-PBX1. The two activation domains of E2A, AD1 and AD2, display redundant, independent, and cooperative functions in a cell-dependent manner. AD1 of E2A functions by binding the transcriptional co-activator CBP/p300; this interaction is required in oncogenesis and occurs between the conserved ϕ-x-x-ϕ-ϕ motif in AD1 and the KIX domain of CBP/p300. However, co-activator recruitment by AD2 has not been characterized. Here, we demonstrate that the first of two conserved ϕ-x-x-ϕ-ϕ motifs within AD2 of E2A interacts at the same binding site on KIX as AD1. Mutagenesis uncovered a correspondence between the KIX-binding affinity of AD2 and transcriptional activation. Although AD2 is dispensable for oncogenesis, experimentally increasing the affinity of AD2 for KIX uncovered a latent potential to mediate immortalization of primary hematopoietic progenitors by E2A-PBX1. Our findings suggest that redundancy between the two E2A activation domains with respect to transcriptional activation and oncogenic function is mediated by binding to the same surface of the KIX domain of CBP/p300.

Epistatic interactions between mutations of TACI (TNFRSF13B) and TCF3 result in a severe primary immunodeficiency disorder and systemic lupus erythematosus

“…We have assessed the relative severity of the disorder of all family members using the clinical score proposed for the use of subcutaneous immunoglobulin/intravenous immunoglobulin, 21 which is based on the frequency and severity of immune sequelae of CVID (Table 1). Application of the Ameratunga et al 2, 19 diagnostic criteria for CVID concluded that the proband (II.2) and her son (III.1) were phenotypically distinct from other family members (clinical score >10) and the highest clinical score was assigned to the proband.…”

“…Nine variants affecting genes with known roles in the immune system were genotyped in the entire kindred (Supplementary Table 3). Of these, only a de novo frameshift nonsense mutation in TCF3 encoding the E2A transcription factors E12 and E47 21 segregated with the two severely symptomatic family members, II.2 and III.1 (Figures 1a and b) in the wider family. TCF3 plays a critical role in early B-cell development.…”

“…Since symptomatic disease is a prerequisite for probable CVID, application of our CVID diagnostic criteria 17,19 concluded that only the proband (II.2) had CVID, while her son (III.1) had reduced IgG levels (symptomatic hypogammaglobulinemia of uncertain significance) and symptomatic IgA deficiency. We have assessed the relative severity of the disorder of all family members using the clinical score proposed for the use of subcutaneous immunoglobulin/intravenous immunoglobulin, 21 which is based on the frequency and severity of immune sequelae of CVID ( Table 1). Application of the Ameratunga et al 2,19 diagnostic criteria for CVID concluded that the proband (II.2) and her son (III.1) were phenotypically distinct from other family members (clinical score 410) and the highest clinical score was assigned to the proband.…”

Components from the human c-myb transcriptional regulation system reactivate epigenetically repressed transgenes

“…Upon further investigation we determined that assembly of the MYB TAD with P300/CBP is critical for Gal4-MYB-mediated activation within Polycomb chromatin. Celastrol inhibits the interaction of p300/CBP with MYB by binding to the CBP KIX domain (74)(75)(76)(77) , and completely reduces Gal4-MYB activity. In contrast, the Gal4-P65 and Gal4-VP64 fusions showed robust activation of PRC-silenced luciferase in the presence of celastrol ( Figure 5B).…”

New insights into transcriptional and leukemogenic mechanisms of AML1-ETO and E2A fusion proteins

“…Both E2A and E2A-Pbx1 recruit p300/CBP via direct and cooperative binding via AD1 and AD2 (Bayly et al, 2004; Denis et al, 2014). AD1 in this context appears to be especially important given that a single mutation of a conserved Leu within PCET, which disrupts p300 interaction, also disrupts the leukemogenic function of E2A-Pbx1 (Bayly et al, 2006).…”