Isolation of an AP-1 repressor by a novel method for detecting protein-protein interactions

Area of Science:

• Molecular Biology
• Cell Signaling
• Gene Regulation

Background:

• Transcription factor AP-1 (Activator Protein-1) is crucial for transducing environmental signals to the transcriptional machinery.
• Tight control over AP-1 target genes is essential, suggesting negative regulation in nonstimulated cells.
• Understanding negative regulators of AP-1 is key to comprehending cellular responses.

Purpose of the Study:

• To identify novel proteins that interact with Jun subunits of AP-1.
• To find proteins that negatively regulate AP-1 activity.
• To develop a novel screen for detecting protein-protein interactions independent of transcriptional readouts.

Main Methods:

• Development of a novel yeast-based Sos recruitment system for detecting protein-protein interactions.
• The system utilizes the recruitment of mammalian guanyl nucleotide exchange factor (GEF) Sos to yeast plasma membrane.
• This recruitment is dependent on a temperature-sensitive Ras GEF, Cdc25-2, enabling growth at nonpermissive temperatures.

Main Results:

• The Sos recruitment system successfully identified new c-Jun-interacting proteins.
• A novel protein, JDP2 (Jun dimerization partner 2), was identified as a c-Jun interactor.
• JDP2 was shown to heterodimerize with c-Jun in nonstimulated cells, leading to repression of AP-1-mediated activation.

Conclusions:

• JDP2 is a novel repressor of AP-1 activity.
• The identified protein-protein interaction mechanism provides a new avenue for studying gene regulation.
• This study elucidates a mechanism for negative regulation of AP-1 in quiescent cells.