Endothelial Cells Express a Novel, Tumor Necrosis Factor-α-regulated Variant of HOXA9*
- From the Department of Cell Biology, Lerner Research Institute of The Cleveland Clinic Foundation, Cleveland, Ohio 44195
Abstract
The expression of the class 1 homeobox (HOX) family of “master control” transcription factors has been studied principally in embryogenesis and neoplasia in which HOX genes play a critical role in cell proliferation, migration, and differentiation. We wished to test whether HOX family members were also involved in a differentiation-like process occurring in normal, diploid adult cells, that is, cytokine-induced activation of endothelial cells (EC). Screening of a human EC cDNA library yielded several members of the A and B groups of HOX transcription factors. One clone represented a novel, alternatively spliced variant of the human HOXA9gene containing a new exon and the expression of which was driven by a novel promoter. This variant termed HOXA9EC appeared restricted to cells of endothelial lineage, i.e. expressed by human EC from multiple sources, but not by fibroblasts, smooth muscle cells, or several transformed cell lines. HOXA9ECmRNA was rapidly down-regulated in EC in response to tumor necrosis factor-α due to an apparent reduction in transcriptional rate. Reporter construct studies showed that the 400 base pairs of genomic DNA directly 5′ to the transcription initiation site ofHOXA9EC contained the information required for both up-regulation in response to cotransfection with a HOXA9ECexpression vector and tumor necrosis factor-α-dependent down-regulation of this gene. These results provide evidence of a novel HOX family member that may participate in either the suppression or the genesis of EC activation.
Footnotes
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↵* This work was supported by National Institutes of Health Grant HL 34727 (to P. E. D.), by an unrestricted grant for cardiovascular research from Berlex Biosciences, and by a grant (to C. V. P.) from the American Heart Association, Northeast Ohio Affiliate.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) AF010258 for the human HOXA9 gene.
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↵‡ To whom correspondence should be addressed: Dept. of Cell Biology-NC10, Cleveland Clinic Lerner Research Institute, 9500 Euclid Ave., Cleveland, OH 44195. Tel.: 216-444-5849; Fax: 216-444-9404; E-mail: dicorlp{at}cesmtp.ccf.org.
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↵2 J. Q. You and P. E. DiCorleto, unpublished results.
- Abbreviations:
- EC
-
endothelial cell
- HOX
-
homeobox
- GST
-
glutathione S-transferase
- EMSA
-
electrophoretic mobility shift assay
- UTR
-
untranslated region
- kb
-
kilobase pair
- bp
-
base pair
- TNF
-
tumor necrosis factor
- RPA
-
RNase protection analysis.
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- Received June 4, 1998.
- Revision received November 4, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
