Regulation of thioredoxin gene expression by vitamin A in human airway epithelial cells

Am J Respir Cell Mol Biol. 2002 May;26(5):627-35. doi: 10.1165/ajrcmb.26.5.4276.


Human thioredoxin (Trx) is a 12-kD protein known to be involved in various reduction/oxidation reactions essential for cell growth and cellular injury repair. We previously demonstrated, based on nuclear run-on assay, that retinoic acid (RA) stimulated Trx gene expression in airway epithelial cells at the transcriptional level. Nucleotide sequencing of the 5'-flanking region of the human Trx gene revealed the presence of a TATA box at -28 and four RA response element (RARE)-like half sites at -426, -453, -507, and -626 nt. Transient transfection assays with a Trx promoter-reporter gene, chloramphenicol acetyltransferase (CAT), demonstrated a dose-dependent involvement of these four RARE-like half sites in RA-enhanced promoter activity. When the DNA fragment that flanks these four RARE-like half sites from -357 to -671 nt was introduced into a heterologous promoter of the tk-CAT2 vector, both basal and RA-stimulated CAT activities were observed. A site-directed mutagenesis approach demonstrated an essential role for RARE-I and RARE-II at -426 and -453 nt, respectively, and an auxiliary role for RARE-III at -507 nt in both basal and RA-stimulated CAT activities. Both in vivo and in vitro genomic footprinting experiments further demonstrated specific protein-DNA interactions in these "putative" RARE-I/II/III half sites. Gel electrophoretic mobility shift assays demonstrated specific interactions of these RARE-like half sites with the nuclear extracts obtained from RA-treated cultures. The anti-RAR-alpha antibody super-shift experiment further confirmed the interactions of RARE-I/II sites with RAR-alpha nuclear receptor. These results suggest a classic RARE/RAR interaction involved in RA-stimulated Trx gene expression in human airway epithelium.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 5' Flanking Region / physiology
  • Cells, Cultured
  • DNA Footprinting
  • Dose-Response Relationship, Drug
  • Electrophoretic Mobility Shift Assay
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects*
  • Epithelial Cells / metabolism*
  • Gene Expression Regulation / drug effects*
  • Genes, Reporter
  • Humans
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Receptors, Retinoic Acid / metabolism
  • Respiratory Mucosa / cytology
  • Respiratory Mucosa / drug effects
  • Respiratory Mucosa / metabolism
  • Response Elements / physiology
  • Retinoic Acid Receptor alpha
  • Sequence Analysis, DNA
  • Thioredoxins / genetics
  • Thioredoxins / metabolism*
  • Transfection
  • Vitamin A / pharmacology*


  • RARA protein, human
  • Receptors, Retinoic Acid
  • Retinoic Acid Receptor alpha
  • Vitamin A
  • Thioredoxins

Associated data

  • GENBANK/AF084048