[Frontiers in Bioscience E2, 1154-1163, June 1, 2010]

Identification and characterization of the promoter of fibroblast activation protein

Jiping Zhang, Matthildi Valianou, Jonathan D. Cheng

Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, PA 19111

TABLE OF CONTENTS

1. Abstract
2. Introduction
Materials and methods
3.1. Cell culture and RNA extraction
3.2. Identification of transcription start site by 5'- Rapid Amplification of cDNA Ends
3.3. Generation of FAP promoter luciferase reporter constructs
3.4. Transient transfection and luciferase assay
3.5. Electrophoretic mobility shift assay
3.6. Small interfering RNA transfection and quantitative RT-PCR
Results
4.1. Sequence analysis of putative FAP promoter region and identification of transcription start site in FAP gene
4.2. Identification and characterization of FAP promoter sequence
4.3. EGR1 binds to FAP promoter and participates in FAP gene transcription
4.4. siRNA-mediated knockdown of EGR1 inhibits the mRNA expression of FAP
5. Discussion
6. Acknowledgemen
7. References

1. ABSTRACT

Fibroblast activation protein (FAP) is a type II integral membrane glycoprotein belonging to the serine protease family. It is selectively expressed by tumor stromal fibroblasts and transiently in the fibroblasts of healing wounds. FAP has been shown to modulate growth, differentiation, adhesion, and metastasis of tumor cells. Despite the importance of FAP in cancer, the mechanisms that govern its expression have not been defined. In this study, we determined the transcription start site of the FAP gene and identified a 2-kb segment with promoter activity in cells expressing FAP. Truncation of this fragment revealed that the core promoter activity resided in a 245-bp fragment surrounding the transcription start site. Electrophoretic mobility shift assay showed that EGR1 binds to the FAP promoter. Mutation of the EGR1 site within this fragment significantly decreased the promoter activity of FAP and eliminated EGR1 binding. Down-regulation of EGR1 resulted in a significant reduction in endogenous FAP mRNA expression. These findings identify the basal transcriptional requirements of FAP gene expression and show EGR1 is an important regulator of FAP expression.