Biochemical Characterization of Diverse Stat5b-Binding Enhancers That Mediate Growth Hormone-Activated Insulin-Like Growth Factor-I Gene Transcription

Ben Varco-Merth, Kasim Mirza, Damir T. Alzhanov, Dennis J. Chia, Peter Rotwein

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

Many of the biological effects of growth hormone (GH) are mediated by insulin-like growth factor I (IGF-I), a 70-amino acid secreted peptide whose gene expression is rapidly induced by GH via the Stat5b transcription factor. We previously identified multiple evolutionarily conserved GH-activated chromosomal binding domains for Stat5b within the rat Igf1 locus, and proposed that they could regulate IGF-I gene activity. Here we investigate the biochemical and functional characteristics of these putative long-range transcriptional enhancers. Each element contained 2 or 3 individual Stat5b recognition sequences that could bind Stat5b in vitro, but with affinities that varied over a >100-fold range. Full transcriptional responsiveness to GH required that all Stat5b sites be intact within an individual enhancer. Replacement of a single lower-affinity Stat5b sequence with a higher-affinity one increased in vitro binding of Stat5b, and boosted transcriptional potency of the entire element to GH. As enhanced transcriptional activity involved changes in only one or two nucleotides within an enhancer DNA segment, there appears to be remarkable specificity and sensitivity in the ability of Stat5b to transform DNA binding activity into transcriptional function. Stat5b was able to stimulate the transcriptional activity of two enhancers in the absence of GH, indicating that individual Stat5b-regulated elements possess distinct functional features. We conclude that combinatorial interplay among multiple Stat5b-binding response elements with distinguishable biochemical properties is responsible for highly regulated control of IGF-I gene activity by GH.

Original languageEnglish (US)
Article numbere50278
JournalPLoS One
Volume7
Issue number11
DOIs
StatePublished - 2012

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Transcription
insulin-like growth factor I
Insulin-Like Growth Factor I
somatotropin
Growth Hormone
transcription (genetics)
Genes
genes
response elements
DNA
Response Elements
Gene expression
functional properties
Rats
Transcription Factors
Nucleotides
transcription factors
nucleotides
peptides
Gene Expression

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Biochemical Characterization of Diverse Stat5b-Binding Enhancers That Mediate Growth Hormone-Activated Insulin-Like Growth Factor-I Gene Transcription. / Varco-Merth, Ben; Mirza, Kasim; Alzhanov, Damir T.; Chia, Dennis J.; Rotwein, Peter.

In: PLoS One, Vol. 7, No. 11, e50278, 2012.

Research output: Contribution to journalArticle

Varco-Merth, Ben ; Mirza, Kasim ; Alzhanov, Damir T. ; Chia, Dennis J. ; Rotwein, Peter. / Biochemical Characterization of Diverse Stat5b-Binding Enhancers That Mediate Growth Hormone-Activated Insulin-Like Growth Factor-I Gene Transcription. In: PLoS One. 2012 ; Vol. 7, No. 11.
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