Hypoxia-inducible factor-1alpha enhances haptoglobin gene expression by improving binding of STAT3 to the promoter.
J Biol Chem
; 286(11): 8857-65, 2011 Mar 18.
Article
em En
| MEDLINE
| ID: mdl-21224490
ABSTRACT
Haptoglobin (Hp) is known to play a role in angiogenesis as well as in anti-inflammation. STAT3 is a major transcription factor for expression of human Hp. We investigated whether hypoxia-inducible factor-1α (HIF-1α), a key mediator of angiogenesis, participates in Hp gene expression. HIF-1α overexpression by gene transfection or hypoxia augmented Hp transcription in HepG2 human hepatoma cells. Conversely, knockdown of HIF-1α by specific siRNA transfection diminished Hp expression, although the level of STAT3 phosphorylation remained unchanged. A luciferase reporter assay using mutant Hp promoters demonstrated that two adjacent DNA elements, a STAT3-binding element (SBE) and a cAMP-response element (CRE)-like site in human Hp promoter -120/-97, were required for HIF-1α-stimulated transactivation of the Hp gene. HIF-1α, STAT3, and p300/CBP were simultaneously bound to the SBE/CRE as a complex form. When HIF-1α was knocked down, STAT3 binding to the SBE in the Hp promoter was attenuated. Our findings suggest that HIF-1α assists STAT3 in strong binding to the proximal SBE in the Hp promoter. The CRE-like site located near the SBE may contribute to the formation of a stable complex of STAT3, HIF-1α, and p300/CBP, which leads to maximum transcription of the Hp gene.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Transcrição Gênica
/
Haptoglobinas
/
Regulação da Expressão Gênica
/
Elementos de Resposta
/
Fator de Transcrição STAT3
/
Subunidade alfa do Fator 1 Induzível por Hipóxia
Limite:
Humans
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
2011
Tipo de documento:
Article