Corticotropin-releasing hormone stimulates proopiomelanocortin transcription by cFos-dependent and -independent pathways: Characterization of an AP1 site in exon

A. L. Boutillier, D. Monnier, D. Lorang, James Lundblad, J. L. Roberts, J. P. Loeffler

Research output: Contribution to journalArticle

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Abstract

The POMC gene, encoding a hormonal precursor protein, is primarily expressed in the pituitary in a tissue-specific manner. The POMC gene is transcriptionally regulated by a variety of hormones and neuropeptides and the second messengers cAMP and Ca++. Using the corticotrope-derived AtT20 cell line, we have previously shown that overexpression of cFos stimulates POMC transcription. The aim of this work was to analyze whether cFos directly interacts with the POMC gene in basal and corticotropin-releasing hormone (CRH) stimulated cells. Using progressively deleted POMC promoter sequences or heterologous promoter constructs coupled to the chloramphenicol acetyl transferase reporter gene, we demonstrate the existence of a major cFos- responsive sequence within the first exon of the POMC gene. This sequence, TGACTAA, appears functionally indistinguishable from the canonical AP1 binding site. When fused to a minimal promoter, this sequence confers inducibility by cFos and CRH. Gel shift analyses with CRH-stimulated AtT20 nuclear extracts or in vitro synthesized proteins revealed that this sequence efficiently binds Fos and Jun. Expression of c-fos anti-sense mRNA reduced CRH-stimulated POMC transcription, thus indicating that, at least in part, cFos mediates the effect of CRH on POMC transcription. However, deletion of this major exonic AP1 site from the POMC constructs greatly reduced the effect of c-fos overexpression but did not suppress POMC stimulation by CRH, indicating that CRH stimulates POMC transcription by one or more cFos-independent mechanism(s).

Original languageEnglish (US)
Pages (from-to)745-755
Number of pages11
JournalMolecular Endocrinology
Volume9
Issue number6
StatePublished - Jun 1995
Externally publishedYes

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Pro-Opiomelanocortin
Corticotropin-Releasing Hormone
Exons
Genes
Protein Precursors
Second Messenger Systems
Electrophoretic Mobility Shift Assay
Chloramphenicol
Transferases
Neuropeptides
Reporter Genes
Binding Sites
Hormones

ASJC Scopus subject areas

  • Molecular Biology
  • Endocrinology, Diabetes and Metabolism

Cite this

Corticotropin-releasing hormone stimulates proopiomelanocortin transcription by cFos-dependent and -independent pathways : Characterization of an AP1 site in exon. / Boutillier, A. L.; Monnier, D.; Lorang, D.; Lundblad, James; Roberts, J. L.; Loeffler, J. P.

In: Molecular Endocrinology, Vol. 9, No. 6, 06.1995, p. 745-755.

Research output: Contribution to journalArticle

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abstract = "The POMC gene, encoding a hormonal precursor protein, is primarily expressed in the pituitary in a tissue-specific manner. The POMC gene is transcriptionally regulated by a variety of hormones and neuropeptides and the second messengers cAMP and Ca++. Using the corticotrope-derived AtT20 cell line, we have previously shown that overexpression of cFos stimulates POMC transcription. The aim of this work was to analyze whether cFos directly interacts with the POMC gene in basal and corticotropin-releasing hormone (CRH) stimulated cells. Using progressively deleted POMC promoter sequences or heterologous promoter constructs coupled to the chloramphenicol acetyl transferase reporter gene, we demonstrate the existence of a major cFos- responsive sequence within the first exon of the POMC gene. This sequence, TGACTAA, appears functionally indistinguishable from the canonical AP1 binding site. When fused to a minimal promoter, this sequence confers inducibility by cFos and CRH. Gel shift analyses with CRH-stimulated AtT20 nuclear extracts or in vitro synthesized proteins revealed that this sequence efficiently binds Fos and Jun. Expression of c-fos anti-sense mRNA reduced CRH-stimulated POMC transcription, thus indicating that, at least in part, cFos mediates the effect of CRH on POMC transcription. However, deletion of this major exonic AP1 site from the POMC constructs greatly reduced the effect of c-fos overexpression but did not suppress POMC stimulation by CRH, indicating that CRH stimulates POMC transcription by one or more cFos-independent mechanism(s).",
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