A dominant negative to activation protein-1 (AP1) that abolishes DNA binding and inhibits oncogenesis

Area of Science:

• Molecular Biology
• Oncogenesis
• Protein Engineering

Background:

• Activation protein-1 (AP1) is a crucial transcription factor regulating cell proliferation and differentiation.
• AP1 functions as a Fos:Jun heterodimer, binding to DNA via basic regions.
• Developing dominant-negative inhibitors is key to understanding and controlling AP1's biological roles.

Purpose of the Study:

• To design and characterize a novel dominant-negative inhibitor of AP1 DNA binding and function.
• To assess the potency and mechanism of the new inhibitor, A-Fos.
• To evaluate the efficacy of A-Fos in interfering with AP1-mediated biological processes in mammalian cells.

Main Methods:

• Protein engineering to create A-Fos by appending an acidic sequence to the Fos leucine zipper.
• Gel shift assays to evaluate A-Fos's inhibition of Fos:Jun heterodimer DNA binding.
• Transient transfection assays to measure inhibition of Jun-dependent transactivation.
• Focus and colony formation assays in mouse fibroblasts to assess biological function inhibition.

Main Results:

• A-Fos effectively inhibits AP1 DNA binding in an equimolar competition.
• A-Fos significantly inhibits Jun-dependent transactivation, with both the acidic extension and Fos leucine zipper being critical.
• A-Fos demonstrates greater potency in inhibiting AP1 biological functions (focus formation) compared to previous dominant-negative strategies.

Conclusions:

• A-Fos is a potent dominant-negative inhibitor of AP1.
• The engineered A-Fos protein provides a powerful tool for dissecting AP1 functions in mammalian cells.
• A-Fos represents an advancement over existing dominant-negative reagents for AP1 inhibition.