Characterization of a delayed early serum response region

Area of Science:

• Molecular Biology
• Gene Regulation
• Cellular Growth

Background:

• The proliferin (PLF) gene promoter serves as a model for studying growth-regulated gene expression.
• Understanding serum-induced gene regulation is crucial for cell growth studies.

Purpose of the Study:

• To identify and characterize the promoter elements responsible for serum-induced regulation of the mouse proliferin (PLF) gene.
• To investigate the protein complexes binding to these elements and their role in gene expression.

Main Methods:

• Analysis of promoter elements, including AP-1 and simian virus 40 (SV40) Sph motif-like repeats.
• Electrophoretic mobility shift assays (EMSAs) to study protein binding.
• Transient cotransfection experiments to assess promoter activity and serum responsiveness.

Main Results:

• Identified an AP-1 site and adjacent SV40 Sph motif-like repeats in the PLF promoter.
• Demonstrated simultaneous binding of distinct protein complexes to both AP-1 and Sph elements.
• Showed that serum stimulation increases protein binding to both elements, conferring synergistic serum responsiveness.
• Identified Fra-1, JunB, and JunD as predominant AP-1 components and found the PLF Sph-binding factor to be distinct from TEF-1.

Conclusions:

• The PLF promoter's serum responsiveness is mediated by synergistic action of AP-1 and Sph elements.
• Specific AP-1 family members and a novel Sph-binding factor are involved in regulating PLF gene expression.
• These findings provide insights into the molecular mechanisms of growth-regulated gene expression.