Autoregulation of fos: the dyad symmetry element as the major target of repression

Area of Science:

• Molecular biology
• Gene regulation
• Cellular signaling

Background:

• The Fos and Jun proteins are transcription factors known to regulate gene expression.
• The fos gene itself is rapidly induced by extracellular signals, such as serum stimulation.
• Understanding the regulatory mechanisms of the fos promoter is crucial for deciphering cellular responses.

Purpose of the Study:

• To investigate the cooperative repression of the fos promoter by Fos and Jun proteins.
• To identify the specific DNA elements responsible for Fos/Jun-mediated repression and basal expression control.
• To elucidate the role of the dyad symmetry element (DSE) in fos gene regulation.

Main Methods:

• Transient cotransfection experiments in NIH3T3 cells to assess promoter activity.
• Stable transfection of NIH3T3 cells to study serum-induced gene expression kinetics.
• Site-directed mutagenesis to remove putative Fos/Jun binding sites and the DSE.

Main Results:

• Removal of all putative Fos/Jun binding sites did not abolish repression by Fos/Jun.
• The dyad symmetry element (DSE) alone was sufficient to mediate repression.
• A specific binding site adjacent to the DSE (-292 to -299) was found to control the basal expression level of the fos promoter.

Conclusions:

• Fos and Jun proteins cooperatively repress the fos promoter through mechanisms involving the DSE.
• While the DSE is critical for repression, a distinct element adjacent to it dictates basal expression levels.
• These findings provide insights into the intricate regulation of the fos gene.