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Papers In Press, published online ahead of print December 1, 2008
J. Lipid Res., doi:10.1194/jlr.M800256-JLR200

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Journal of Lipid Research, Vol. 49, 2590-2604, December 2008
Copyright © 2008 by American Society for Biochemistry and Molecular Biology

Regulation of the human thromboxane A₂ receptor gene by Sp1, Egr1, NF-E2, GATA-1, and Ets-1 in megakaryocytes

AnneMarie M. Gannon and B. Therese Kinsella¹

University College Dublin School of Biomolecular and Biomedical Sciences, University College Dublin Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland

Published, JLR Papers in Press, August 12, 2008.

This work was supported by The Wellcome Trust, The Health Research Board and Science Foundation Ireland.

¹ To whom correspondence should be addressed. e-mail: Therese.Kinsella{at}UCD.IE

The and β isoforms of the human thromboxane A₂ (TXA₂) receptor (TP) are encoded by a single gene but are transcriptionally regulated by distinct promoters, termed promoter 1 (Prm1) and Prm3, respectively. Herein, it was sought to identify factors regulating Prm1 within the megakaryocytic human erythroleukemia 92.1.7 cell line. Through gene deletion and reporter assays, the core Prm1 was localized to between nucleotides –6,320 and –5,895, proximal to the transcription initiation site. Furthermore, two upstream repressor and two upstream activator regions were identified. Site-directed mutagenesis of four overlapping Sp1/Egr1 elements and an NF-E2/AP1 element within the proximal region substantially reduced Prm1 activity. Deletion/mutation of GATA and Ets elements disrupted the upstream activator sequence located between –7,962 and –7,717, significantly impairing Prm1 activity. Electrophoretic mobility shift assays and chromatin immunoprecipitations confirmed that Sp1, Egr1, and NF-E2 bind to elements within the core promoter, whereas GATA-1 and Ets-1 factors bind to the upstream activator sequence (between –7,962 and –7,717). Collectively, these data establish that Sp1, Egr1, and NF-E2 regulate core Prm1 activity in the megakaryocytic-platelet progenitor cells, whereas GATA-1 and Ets-1 act as critical upstream activators, hence providing the first genetic basis for the expression of the human TXA₂ receptor (TP) within the vasculature.

Supplementary key words promoter • transcription • prostanoid • platelet

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