Inhibition of p300/CBP by early B-cell factor.
Early B-cell factor (EBF) is a DNA binding protein required for early B-cell development. It activates transcription of several B-cell-specific genes, including the lambda5 gene, which encodes a protein necessary for signaling by the pre-B-cell receptor. In an effort to understand the mechanism by which EBF activates transcription, we examined its interaction with the coactivator protein p300/CBP. We found that two domains of EBF each bind the histone acetyltransferase (HAT)/CH3 domain of p300/CBP both in vitro and in vivo. Surprisingly, transcriptional activation by EBF was not sensitive to E1A, a potent p300/CBP inhibitor. In fact, overexpressed EBF mimicked E1A by severely repressing the activity of several other transcription factors, including E47, a protein that acts cooperatively with EBF to promote transcription of the lambda5 gene. This broad inhibitory profile correlated with EBF's ability to repress the HAT activity of p300/CBP in vivo and in vitro. However, such a repressed complex is not likely to form at the lambda5 promoter in vivo since (i) EBF could not bind p300/CBP and DNA simultaneously and (ii) the cooperativity imparted by E47 was sensitive to E1A. Our data reveal an intriguing inhibitory property of EBF-a property shared only by E1A, Twist, Pu.1, and the Hox family of homeodomain proteins-and suggest that E47 and EBF play distinct roles during lambda5 promoter activation.
Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6145, USA.
Fang
F
Zhao
Ruth
R
McCarrick-Walmsley
Peter
P
Akerblad
Mikael
M
Sigvardsson
Tom
T
Kadesch
D016475:3T3 Cells; D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050881:E1A-Associated p300 Protein; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D017930:Genes, Reporter; D051548:Histone Acetyltransferases; D051379:Mice; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010950:Plasma Cells / Q000166:cytology / Q000502:physiology; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; C489921:Ebf1 protein, mouse; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D000123:Acetyltransferases; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse; D051548:Histone Acetyltransferases