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JunD and HIF‐1α mediate transcriptional activation of angiotensinogen by TGF‐β1 in human lung fibroblasts
Author(s) -
Abdul-Hafez Amal,
Shu Ruijie,
Uhal Bruce D.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.08-114611
Subject(s) - chromatin immunoprecipitation , gene knockdown , microbiology and biotechnology , luciferase , messenger rna , transcription (linguistics) , chemistry , transforming growth factor , transcription factor , promoter , reporter gene , biology , gene expression , transfection , gene , biochemistry , linguistics , philosophy
Earlier work showed that TGF‐β 1 potently increases angiotensinogen (AGT) gene mRNA in primary human lung fibroblasts. Here the mechanism of TGF‐β 1‐induced AGT expression was studied in the IMR90 human lung fibroblast cell line. The increase in AGT mRNA induced by TGF‐β 1 was completely blocked by actinomycin‐D. TGF‐β 1 increased the activity of a full‐length human AGT promoter‐luciferase reporter (AGT‐LUC) but did not alter AGT mRNA half‐life. Serial deletion analyses revealed that 67% of TGF‐β‐inducible AGT‐LUC activity resides in a small domain of the AGT core promoter;this domain contains binding sites for hypoxia‐inducible factor (HIF)‐1 and activationprotein‐1 (AP‐1) transcription factors. TGF‐β1 increasedHIF‐1α protein abundance and the activity of a hypoxia‐responsive element reporter;overexpression ofHIF‐1 increased basal AGT‐LUC activity. Both oligonucleotide pulldown and chromatin immunoprecipita‐tion assays revealed increased binding of JunD andHIF‐1 α to the AGT core promoter in response to TGF‐β1. TGF‐β1‐inducible AGT‐LUC was reduced by anAP‐1 dominant negative or by mutation of theAP‐1 site. Knockdown of either JunD orHIF‐1α individually by siRNA partially reduced AGT‐LUC. In contrast, simultaneous knockdown of both JunD andHIF‐1α completely eliminated TGF‐β 1‐inducible AGT‐LUC activity. These data suggest that TGF‐β 1 up‐regulates AGT transcription in human lung fibroblasts through a mechanism that requires both JunD andHIF‐1α binding to the AGT core promoter. They also suggest a molecular mechanism linking hypoxia signaling and fibrogenic stimuli in the lungs.—Abdul‐Hafez, A.,Shu, R., Uhal, B.D. JunD andHIF‐1a mediate transcriptional activation of angiotensinogen by TGF‐P 1 in human lung fibroblasts. FASEB J. 23, 1655–1662 (2009)