title: E2A proteins enhance the histone acetyltransferase activity of the transcriptional co-activators CBP and p300.
abstract: The E2A gene encodes the E-protein transcription factors E12 and E47 that play critical roles in B-lymphopoiesis. A somatic chromosomal translocation detectable in 5% of cases of acute lymphoblastic leukemia (ALL) involves E2A and results in expression of the oncogenic transcription factor E2A-PBX1. CREB binding protein (CBP) and its close paralog p300 are transcriptional co-activators with intrinsic histone acetyltransferase (HAT) activity. We and others have shown that direct binding of an N-terminal transcriptional activation domain present in E12/E47 and E2A-PBX1 to the KIX domain of CBP/p300 contributes to E2A protein function. In the current work we show for the first time that the catalytic HAT activity of CBP/p300 is increased in the presence of residues 1-483 of E2A (i.e., the portion present in E2A-PBX1). The addition of purified, recombinant E2A protein to in vitro assays results in a two-fold augmentation of CBP/p300 HAT activity, whereas in vivo assays show a ten-fold augmentation of HAT-dependent transcriptional induction and a five-fold augmentation of acetylation of reporter plasmid-associated histone by CBP in response to co-transfected E2A. Our results indicate that the HAT-enhancing effect is independent of the well-documented E2A-CBP interaction involving the KIX domain and suggest a role for direct, perhaps low affinity binding of E2A to a portion of CBP that includes the HAT domain and flanking elements. Our findings add to a growing body of literature indicating that interactions between CBP/p300 and transcription factors can function in a specific manner to modulate HAT catalytic activity.
authors.affiliation: Department of Pathology and Molecular Medicine, Queen's University, Canada.
authors.forename: Brandy D
authors.initials: BD
authors.lastname: Hyndman
authors.forename: Patrick
authors.initials: P
authors.lastname: Thompson
authors.forename: Richard
authors.initials: R
authors.lastname: Bayly
authors.forename: Graham P
authors.initials: GP
authors.lastname: Côté
authors.forename: David P
authors.initials: DP
authors.lastname: LeBrun
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D050882:CREB-Binding Protein / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D051548:Histone Acetyltransferases / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000378:metabolism; D006801:Humans; D015514:Oncogene Proteins, Fusion / Q000378:metabolism; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D015533:Transcriptional Activation; D050880:p300-CBP Transcription Factors / Q000378:metabolism; D000099224:p300-CBP-Associated Factor
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D050882:CREB-Binding Protein; D051548:Histone Acetyltransferases; D018398:Homeodomain Proteins; D015514:Oncogene Proteins, Fusion; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C407909:TCF3 protein, human; C089847:E2A-Pbx1 fusion protein; C494363:CREBBP protein, human