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The EGF response element in the prolactin promoter
K K Jacob1, E Wininger, K DiMinni
1Department of Medicine, New York University Medical Center, NY 10016, USA.
Molecular and Cellular Endocrinology
|August 4, 1999
Summary
Epidermal growth factor (EGF) signaling in GH4 cells involves a specific promoter region that binds Ets-related transcription factors. This mechanism for increasing prolactin gene expression differs from insulin or cAMP signaling.
Area of Science:
- Molecular Biology
- Cellular Signaling
- Gene Regulation
Background:
- Epidermal growth factor (EGF) is known to stimulate prolactin gene expression in GH4 cells.
- The specific promoter elements mediating this EGF response have not been fully elucidated.
- Previous studies identified a cAMP/insulin response element in the prolactin promoter.
Purpose of the Study:
- To identify and characterize the promoter elements responsible for EGF-induced prolactin gene expression.
- To investigate the signaling pathway utilized by EGF in regulating prolactin transcription.
- To determine if EGF signaling converges with insulin or cAMP pathways.
Main Methods:
- Deletion and linker-scanning mutagenesis of the rat prolactin promoter.
- Reporter gene assays (prolactin-CAT) in GH4 cells.
- Analysis of transcription factor binding and inhibition using dominant-negative constructs (c-Ets-1 DNA-binding domain).
Main Results:
- A bipartite element (-96/-87, -76/-67) in the rat proximal prolactin promoter was identified as essential for EGF signaling.
- This element, previously identified as a cAMP/insulin response element, mediated EGF-induced transcription in a orientation-independent manner when transferred to a heterologous promoter.
- EGF's effects were additive to insulin or cAMP, suggesting a distinct mechanism.
- The EGF response element serves as a recognition site for Ets-related transcription factors.
- Inhibition of Ets-related factors with c-Ets-1 dominant-negative construct reduced EGF-induced prolactin-CAT expression by 65%.
Conclusions:
- EGF activates prolactin gene transcription through a specific bipartite element in the proximal promoter.
- This EGF response element is recognized by Ets-related transcription factors.
- EGF and insulin may utilize Ets-related transcription factors to activate prolactin gene transcription via the same promoter element, despite distinct signaling mechanisms.