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Mol. Cell. Biol., Mar 1997, 1407-1416, Vol 17, No. 3
X Cheng, MJ Reginato, NC Andrews and MA Lazar
Thyroid hormone (T3) and retinoic acid (RA) play important roles in
erythropoiesis. We found that the hematopoietic cell-specific bZip protein
p45/NF-E2 interacts with T3 receptor (TR) and RA receptor (RAR) but not
retinoid X receptor. The interaction is between the DNA-binding domain of
the nuclear receptor and the leucine zipper region of p45/NF- E2 but is
markedly enhanced by cognate ligand. Remarkably, ligand- dependent
transactivation by TR and RAR is markedly potentiated by p45/NF-E2. This
effect of p45/NF-E2 is prevented by maf-like protein p18, which functions
positively as a heterodimer with p45/NF-E2 on DNA. Potentiation of hormone
action by p45/NF-E2 requires its activation domain, which interacts
strongly with the multifaceted coactivator cyclic AMP response element
protein-binding protein (CBP). The region of CBP which interacts with
p45/NF-E2 is the same interaction domain that mediates inhibition of
hormone-stimulated transcription by AP1 transcription factors.
Overexpression of the bZip interaction domain of CBP specifically abolishes
the positive cross talk between TR and p45/NF-E2. Thus, positive cross talk
between p45/NF-E2 and nuclear hormone receptors requires direct
protein-protein interactions between these factors and with CBP, whose
integration of positive signals from two transactivation domains provides a
novel mechanism for potentiation of hormone action in hematopoietic cells.
Copyright © 1997, American Society for Microbiology
The transcriptional integrator CREB-binding protein mediates positive cross talk between nuclear hormone receptors and the hematopoietic bZip protein p45/NF-E2
Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104-6149, USA.
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