title: Expression of DDX3 is directly modulated by hypoxia inducible factor-1 alpha in breast epithelial cells.
abstract: DEAD box protein, DDX3, is aberrantly expressed in breast cancer cells ranging from weakly invasive to aggressive phenotypes and functions as an important regulator of cancer cell growth and survival. Here, we demonstrate that hypoxia inducible factor-1α is a transcriptional activator of DDX3 in breast cancer cells. Within the promoter region of the human DDX3 gene, we identified three putative hypoxia inducible factor-1 responsive elements. By luciferase reporter assays in combination with mutated hypoxia inducible factor-1 responsive elements, we determined that the hypoxia inducible factor-1 responsive element at position -153 relative to the translation start site is essential for transcriptional activation of DDX3 under hypoxic conditions. We also demonstrated that hypoxia inducible factor-1 binds to the DDX3 promoter and that the binding is specific, as revealed by siRNA against hypoxia inducible factor-1 and chromatin immunoprecipitation assays. Thus, the activation of DDX3 expression during hypoxia is due to the direct binding of hypoxia inducible factor-1 to hypoxia responsive elements in the DDX3 promoter. In addition, we observed a significant overlap in the protein expression pattern of hypoxia inducible factor-1α and DDX3 in MDA-MB-231 xenograft tumors. Taken together, our results demonstrate, for the first time, the role of DDX3 as a hypoxia-inducible gene that exhibits enhanced expression through the interaction of hypoxia inducible factor-1 with hypoxia inducible factor-1 responsive elements in its promoter region.
authors: Department of Radiology and Radiological Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors: Mahendran
authors: M
authors: Botlagunta
authors: Balaji
authors: B
authors: Krishnamachary
authors: Farhad
authors: F
authors: Vesuna
authors: Paul T
authors: PT
authors: Winnard
authors: Guus M
authors: GM
authors: Bol
authors: Arvind H
authors: AH
authors: Patel
authors: Venu
authors: V
authors: Raman
mesh_terms: D000818:Animals; D001483:Base Sequence; D001940:Breast / Q000473:pathology*; D015687:Cell Hypoxia / Q000187:drug effects; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D003035:Cobalt / Q000494:pharmacology; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D020218:Response Elements / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D003035:Cobalt; C119332:DDX3X protein, human; D053487:DEAD-box RNA Helicases; C018021:cobaltous chloride