Functional antagonism between oncoprotein c-Jun and the glucocorticoid receptor

Area of Science:

• Molecular Biology
• Gene Regulation
• Transcription Factors

Background:

• Glucocorticoid receptor (GR) and Jun/AP-1 are key transcription factors involved in cellular processes.
• Understanding their interactions is crucial for deciphering complex gene regulatory networks.

Purpose of the Study:

• To investigate the regulatory relationship between GR and Jun/AP-1.
• To elucidate the mechanism by which these factors influence each other's transcriptional activity.

Main Methods:

• Overexpression studies of c-Jun and GR.
• Analysis of gene activation using reporter assays with glucocorticoid response elements (GREs).
• Mutant analysis of GR and c-Jun domains.
• Gel retardation assays to assess DNA-protein complex formation.

Main Results:

• Overexpression of c-Jun blocked GR-mediated gene activation at GREs.
• GR repressed AP-1-driven transcriptional activation.
• Ligand binding and DNA binding domains of GR, and the leucine zipper region of c-Jun, were essential for repression.
• Bacterially expressed c-Jun interfered with GR binding to GREs.

Conclusions:

• GR and Jun/AP-1 exhibit reciprocal repression of transcriptional activation.
• This interaction is mediated by a novel mechanism independent of direct DNA binding, likely involving protein-protein interactions.
• These findings reveal a new layer of complexity in the regulation of gene expression by distinct transcription factor classes.