Essential AP-1 and PEA3 binding elements in the human urokinase enhancer display cell type-specific activity

Area of Science:

• Molecular Biology
• Gene Regulation
• Cancer Research

Background:

• The urokinase-type plasminogen activator (uPA) gene plays a critical role in cell migration and tissue remodeling.
• Dysregulation of uPA is implicated in various pathological conditions, including cancer metastasis.
• Understanding the transcriptional regulation of uPA is crucial for developing targeted therapies.

Purpose of the Study:

• To characterize a transcriptional enhancer controlling human uPA gene expression.
• To identify transcription factor binding sites within the enhancer region.
• To elucidate the differential activity of these sites in various cancer cell lines.

Main Methods:

• Reporter gene assays (transient transfection) were used to assess enhancer activity.
• DNase footprinting and gel retardation assays identified transcription factor binding sites.
• Deletions, point mutations, and subcloned fragments were analyzed to determine the role of specific sites.

Main Results:

• A transcriptional enhancer located 2 kbp upstream of the uPA mRNA cap site was identified and found active in HeLa, HepG2, and HT1080 cell lines.
• The enhancer contains binding sites for transcription factor AP-1 (fos/jun) and PEA3 (ets/Spi).
• Differential activity of AP-1 and AP-1/PEA3 binding sites was observed across the cell lines, with AP-1 dominating in HeLa and AP-1/PEA3 in HT1080 and HepG2 cells.

Conclusions:

• The identified enhancer and its AP-1 and PEA3 binding sites are critical for uPA gene regulation.
• Cell-specific activity of these binding sites contributes to differential uPA expression.
• Findings provide insights into uPA regulation by oncogenes and other factors, relevant to cancer biology.