BR22, a 26 kDa thyroid transcription factor-1 associated protein (TAP26), is expressed in human lung cells

M. C W Yang, B. Wang, J. C. Weissler, L. R. Margraf, Yih Sheng Yang

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The current authors have previously identified BR22, a thyroid transcription factor (TTF)-1 associated protein 26 (TAP26), which interacts with TTF-1 to enhance human surfactant protein (SP)-B promoter activity in transfected 293 cells. However, the expression of TAP26 in the lung cells and its biological relevance to the SP-B production under physiological conditions were not examined. In this study, endogenous co-immunoprecipitation and in situ immunohistochemical staining techniques were employed to explore the presence of TAP26 and TTF-1 complex in the lung epithelial cells. The correlation of TAP26, TTF-1 and SP-B expression was inspected in H441 cells in the presence of dexamethasone, a known positive effector of the SP-B promoter. Monoclonal antibody (mAb) against TAP26 can co-immunoprecipitate both TAP26 and TTF-1 from H441 cells. Using this antibody in in situ staining of human lung sections, the data show that TAP26 is present in the lung alveolar epithelial cells. Reverse transcriptase-polymerase chain reaction and Western blot analyses of type-II cells as well as dexamethasone-treated H441 cells suggest that TAP26 expression is modulated coordinately with SP-B and TTF-1 in these cells. In summary, the current study demonstrates that thyroid transcription factor-1 associated protein 26 is an associated protein of thyroid transcription factor-1 in the lung alveolar epithelial cells where surfactant protein gene expressions take place in vivo.

Original languageEnglish (US)
Pages (from-to)28-34
Number of pages7
JournalEuropean Respiratory Journal
Issue number1
Publication statusPublished - Jul 1 2003



  • BR22
  • Surfactant protein B
  • Thyroid transcription factor-1
  • Thyroid transcription factor-1 associated protein 26

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine

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