Negative regulation of human growth hormone gene expression by insulin is dependent on hypoxia-inducible factor binding in primary non-tumor pituitary cells.
J Biol Chem
; 287(40): 33282-92, 2012 Sep 28.
Article
em En
| MEDLINE
| ID: mdl-22833680
ABSTRACT
Insulin controls growth hormone (GH) production at multiple levels, including via a direct effect on pituitary somatotrophs. There are no data, however, on the regulation of the intact human (h) GH gene (hGH1) by insulin in non-tumor pituitary cells, but the proximal promoter region (nucleotides -496/+1) responds negatively to insulin in transfected pituitary tumor cells. A DNA-protein interaction was also induced by insulin at nucleotides -308/-235. Here, we confirmed the presence of a hypoxia-inducible factor 1 (HIF-1) binding site within these sequences (-264/-259) and investigated whether HIF-1 is associated with insulin regulation of "endogenous" hGH1. In the absence of primary human pituitary cells, transgenic mice expressing the intact hGH locus in a somatotroph-specific manner were generated. A significant and dose-dependent decrease in hGH and mouse GH RNA levels was detected in primary pituitary cell cultures from these mice with insulin treatment. Increasing HIF-1α availability with a hypoxia mimetic significantly decreased hGH RNA levels and was accompanied by recruitment of HIF-1α to the hGH1 promoter in situ as seen with insulin. Both inhibition of HIF-1 DNA binding by echinomycin and RNA interference of HIF-1α synthesis blunted the negative effect of insulin on hGH1 but not mGH. The insulin response is also sensitive to histone deacetylase inhibition/trichostatin A and associated with a decrease in H3/H4 hyperacetylation in the proximal hGH1 promoter region. These data are consistent with HIF-1-dependent down-regulation of hGH1 by insulin via chromatin remodeling specifically in the proximal promoter region.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Hipófise
/
Hormônio do Crescimento Humano
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Insulina
/
Hipóxia
Tipo de estudo:
Prognostic_studies
Limite:
Animals
/
Female
/
Humans
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Male
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article