A CRE-like element plays an essential role in cAMP regulation of human SP-A2 gene in alveolar type II cells

Pampee Paul Young, Carole R. Mendelson

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The human has two genes encoding surfactant protein-A (SP-A), termed SP- A1 and SP-A2; the SP-A2 gene is more highly regulated by cAMP and during fetal development than is SP-A1. In this study, by use of primary cultures of human type II cells transfected with fusion genes containing various amounts of SP-A2 5'-flanking DNA linked to human growth hormone (hGH) structural gene, as reporter, we found that -296 bp of SP-A2 upstream sequence is sufficient to direct high basal and cAMP-inducible expression in type II cells, but not in other cell types. By use of competitive EMSA, we observed that nuclear proteins isolated from midtrimester human fetal lung tissue bind specifically to a cAMP response element (CRE)-like sequence, TGACCTTA, at - 242 bp, which we have termed CRE(SP-A2). Binding activity of CRE(SP-A2) for nuclear proteins from human fetal lung tissue before culture was manifest as two complexes of different mobilities and equivalent intensity. By contrast, upon differentiation of the human fetal lung in culture in the presence of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), the higher mobility complex was decreased to undetectable levels. By UV cross-linking analysis, using nuclear extracts from midgestation human fetal lung before culture and radiolabeled CRE(SP-A2) as a probe, we observed binding of proteins of ~50, 36, and 30 kDa. When nuclear extracts from human fetal lung cultured in the presence of DBcAMP were analyzed, binding of only the 50- and 36-kDa proteins was apparent. On the other hand, when the canonical CRE (TGACGTCA) known to bind the transcription factor CREB (M(r) ≃ 43,000) was used as a probe, binding of only a ~43-kDa protein was evident using nuclear extracts from human fetal lung before and after culture. In type II cells transfected with an SP-A2 296:hGH fusion gene in which CRE(SP-A2) was mutated, there was a marked reduction of basal and cAMP-stimulated fusion gene expression. These findings indicate that CRE(SP-A2) serves an important role in mediating basal and cAMP-inducible expression of the human SP-A2 gene in type II cells, that the fetal lung nuclear proteins bound to CRE(SP-A2) differ from those bound to the canonical palindromic CRE, and that changes in the complex of nuclear proteins bound to CRE(SP-A2) accompany induction of SP-A gene expression.

Original languageEnglish (US)
Pages (from-to)L287-L299
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Issue number2 15-2
StatePublished - Aug 1996


  • adenosine 3',5'- cyclic monophosphate
  • gene expression
  • human fetal lung
  • surfactant protein
  • type II pneumonocytes

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology


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