Characterization of distinct Stat5b binding sites that mediate growth hormone-stimulated IGF-I gene transcription

Dennis J. Chia, Mitsuru Ono, Joachim Woelfle, Mylynda Schlesinger-Massart, Honglin Jiang, Peter Rotwein

Research output: Contribution to journalArticle

66 Scopus citations

Abstract

A key agent in the anabolic actions of growth hormone (GH) is insulin-like growth factor-I (IGF-I), a 70-amino acid secreted protein with direct effects on somatic growth and tissue maintenance and repair. GH rapidly and potently stimulates IGF-I gene transcription by mechanisms independent of new protein synthesis, and recent studies have linked the transcription factor Stat5b to a regulatory network connecting the activated GH receptor on the cell membrane to the IGF-I gene in the nucleus. Here we analyze two distinct conserved GH response elements in the rat IGF-I locus that contain paired Stat5b sites. Each response element binds Stat5b in vivo in a GH-dependent way, as assessed by chromatin immunoprecipitation assays, and consists of one high affinity and one lower affinity Stat5b site, as determined by both qualitative and quantitative protein-DNA binding studies. In biochemical reconstitution experiments, both response elements are able to mediate GH-stimulated and Stat5b-dependent transcription when fused to a reporter gene containing either the major IGF-I promoter or aminimal neutral promoter, although the paired Stat5b sites located in the second IGF-I intron were more than twice as effective as the response element that mapped ∼73 kb 5′ to the IGF-I exon 1. Taken together, our results define the initial molecular architecture of a complicated GH-regulated transcriptional pathway, and suggest that apparently redundant hormone response elements provide amechanism for amplifying GH action at a physiologically important target gene.

Original languageEnglish (US)
Pages (from-to)3190-3197
Number of pages8
JournalJournal of Biological Chemistry
Volume281
Issue number6
DOIs
StatePublished - Feb 10 2006

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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