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Dispersed Chromosomal Stat5b-binding elements mediate growth hormone-activated insulin-like growth factor-I gene transcription.

ABSTRACT: The growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis regulates somatic growth during childhood and orchestrates tissue repair throughout the life span. Recently described inactivating mutations in Stat5b in humans with impaired growth have focused attention on this transcription factor as a key agent linking GH-stimulated signals to IGF-I gene expression, and several putative Stat5b sites have been identified in the IGF-I gene. Here, we define and characterize potential GH- and Stat5b-activated chromosomal enhancers that can regulate IGF-I gene transcription. Of 89 recognizable Stat5 sequences in 200 kb centering on the rat IGF-I gene, 22 resided within conserved regions and/or were identical among different species. Only 15 of these sites, organized into 7 distinct domains, were found to bind Stat5b by quantitative chromatin immunoprecipitation assays in liver chromatin of rats, but only after acute GH treatment. These sites could bind Stat5b in vitro, and individual domains could mediate GH- and Stat5b-stimulated IGF-I promoter activity in cultured cells. Further analyses revealed that four Stat5b domains possessed chromatin signatures of enhancers, including binding of co-activators p300 and Med1, and RNA polymerase II. These modifications preceded GH-stimulated recruitment of Stat5b, as did lysine 4 monomethylation of histone H3, which was enriched in 6/7 Stat5b-binding elements. In contrast, histone acetylation was induced by GH but was limited to Stat5b binding domains found within the IGF-I transcription unit. We conclude that GH stimulates recruitment of Stat5b to multiple dispersed regions within the igf1 locus, including several with properties consistent with long range transcriptional enhancers that collectively regulate GH-activated IGF-I gene transcription.

SUBMITTER: Chia DJ

PROVIDER: S-EPMC2878528 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Dispersed Chromosomal Stat5b-binding elements mediate growth hormone-activated insulin-like growth factor-I gene transcription.

Chia Dennis J DJ Varco-Merth Ben B Rotwein Peter P

The Journal of biological chemistry 20100407 23

The growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis regulates somatic growth during childhood and orchestrates tissue repair throughout the life span. Recently described inactivating mutations in Stat5b in humans with impaired growth have focused attention on this transcription factor as a key agent linking GH-stimulated signals to IGF-I gene expression, and several putative Stat5b sites have been identified in the IGF-I gene. Here, we define and characterize potential GH- and Stat ...[more]

PMID: 20378540

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Project description:The transcription factor Nrf2 (encoded by Nfe2l2) induces expression of numerous detoxifying and antioxidant genes in response to oxidative stress. The cytoplasmic protein Keap1 interacts with and represses Nrf2 function. Computational approaches were developed to identify factors that modulate Nrf2 in a mouse liver gene expression compendium. Forty-eight Nrf2 biomarker genes were identified using profiles from the livers of mice in which Nrf2 was activated genetically in Keap1-null mice or chemically by a potent activator of Nrf2 signaling. The rank-based Running Fisher statistical test was used to determine the correlation between the Nrf2 biomarker genes and a test set of 81 profiles with known Nrf2 activation status demonstrating a balanced accuracy of 96%. For a large number of factors examined in the compendium, we found consistent relationships between activation of Nrf2 and feminization of the liver transcriptome through suppression of the male-specific growth hormone (GH)-regulated transcription factor STAT5b. The livers of female mice exhibited higher Nrf2 activation than male mice in untreated or chemical-treated conditions. In male mice, Nrf2 was activated by treatment with ethinyl estradiol, whereas in female mice, Nrf2 was suppressed by treatment with testosterone. Nrf2 was activated in 5 models of disrupted GH signaling containing mutations in Pit1, Prop1, Ghrh, Ghrhr, and Ghr. Out of 59 chemical treatments that activated Nrf2, 36 exhibited STAT5b suppression in the male liver. The Nrf2-STAT5b coupling was absent in in vitro comparisons of chemical treatments. Treatment of male and female mice with 11 chemicals that induce oxidative stress led to activation of Nrf2 to greater extents in females than males. The enhanced basal and inducible levels of Nrf2 activation in females relative to males provides a molecular explanation for the greater resistance often seen in females vs. males to age-dependent diseases and chemical-induced toxicity.

Dataset Information

Dispersed Chromosomal Stat5b-binding elements mediate growth hormone-activated insulin-like growth factor-I gene transcription.

Publications

Dispersed Chromosomal Stat5b-binding elements mediate growth hormone-activated insulin-like growth factor-I gene transcription.

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