Related Experiment Videos
Contextual dependence of steroid receptor function on an androgen-responsive enhancer
A Scheller1, R I Scheinman, E Thompson
1Department of Human Genetics, University of Michigan Medical Center, Ann Arbor 48109-0618, USA.
Molecular and Cellular Endocrinology
|July 23, 1996
Summary
This study reveals how specific DNA sequences and the NF-kappa B protein influence the differential activation of the sex-limited protein (Slp) gene by androgens and glucocorticoids. Understanding these interactions is key to steroid hormone action.
Area of Science:
- Molecular Biology
- Endocrinology
- Gene Regulation
Background:
- Steroid hormones regulate gene expression through specific receptors and DNA elements.
- The sex-limited protein (Slp) gene enhancer contains a hormone response element (HRE) crucial for steroid induction.
- Differential gene activation by androgens and glucocorticoids suggests complex regulatory mechanisms.
Purpose of the Study:
- To identify DNA elements and transcription factors responsible for differential steroid activation of the Slp gene enhancer.
- To elucidate the distinct roles of androgen receptor (AR) and glucocorticoid receptor (GR) in regulating Slp gene expression.
- To investigate the contribution of NF-kappa B to steroid-mediated Slp gene induction.
Main Methods:
- Site-directed mutagenesis of Slp gene enhancer fragments (C' delta 2 and C' delta 9).
- Transfection assays to measure reporter gene activity in response to androgens and glucocorticoids.
- DNase I footprinting to assess receptor binding to DNA.
- Functional analysis involving I kappa B expression to evaluate NF-kappa B's role.
Main Results:
- Mutations in the HRE and an octamer-like sequence differentially affected GR and AR activity, with GR being more sensitive.
- An HRE half-site was critical for androgen-specific induction of the C' delta 9 fragment.
- NF-kappa B bound to a region present in C' delta 2 but absent in C' delta 9, and its presence modulated steroid response, indicating a permissive role in steroid activation.
Conclusions:
- Differential interactions of AR and GR with specific DNA sites, including nonconsensus elements, contribute to distinct steroid responses.
- NF-kappa B plays a permissive role in steroid-mediated Slp gene activation, influencing the assembly of transcription complexes.
- The interplay between steroid receptors, DNA elements, and other transcription factors like NF-kappa B is crucial for precise hormonal regulation of gene expression.