A Polymorphism of the Human Matrix γ-Carboxyglutamic Acid Protein Promoter Alters Binding of an Activating Protein-1 Complex and Is Associated with Altered Transcription and Serum Levels

• Published in: The Journal of biological chemistry Vol. 276; no. 35; pp. 32466 - 32473
• Main Authors: Farzaneh-Far, Afshin, Davies, John D., Braam, Levienja A., Spronk, Henri M., Proudfoot, Diane, Chan, Shiu-Wan, O'Shaughnessy, Kevin M., Weissberg, Peter L., Vermeer, Cees, Shanahan, Catherine M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 31.08.2001
• Subjects: Animals; Aorta; Binding Sites; Calcium-Binding Proteins - chemistry; Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - metabolism; Cell Nucleus - metabolism; Cells, Cultured; Chondrocytes - metabolism; Extracellular Matrix Proteins - chemistry; Extracellular Matrix Proteins - genetics; Extracellular Matrix Proteins - metabolism; Gene Expression Regulation; Humans; Matrix ^g-carboxyglutamic acid protein; Matrix Gla Protein; MGP protein; Muscle, Smooth, Vascular - metabolism; Polymorphism, Genetic; Polymorphism, Single-Stranded Conformational; Promoter Regions, Genetic; Rats; Rats, Wistar; Recombinant Fusion Proteins - metabolism; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Tetradecanoylphorbol Acetate - pharmacology; Transcription Factor AP-1 - chemistry; Transcription Factor AP-1 - metabolism; Transcription, Genetic; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M104909200

Matrix γ-carboxyglutamic acid protein (MGP) is a mineral-binding extracellular matrix protein synthesized by vascular smooth muscle cells (VSMCs) and chondrocytes that is thought to be a key regulator of tissue calcification. In this study, we identified four polymorphisms in the promoter region of the human MGP gene. Transfection studies showed that the G−7A and T−138C polymorphisms have an important impact on in vitro promoter activity when transiently transfected into VSMCs. We found that one of these polymorphisms (T−138C) is significantly correlated with serum MGP levels in human subjects. Promoter deletion analysis showed that this polymorphism lies in a region of the promoter critical for transcription in VSMCs. This region contains a potential activating protein-1 (AP-1) binding element located between −142 and −136. We have demonstrated that the T−138C polymorphism results in altered binding of an AP-1 complex to this region. The −138T allelic variant binds AP-1 complexes consisting primarily of c-Jun, JunB and its partners Fra-1 and Fra-2 in rat VSMC. Furthermore, the −138T variant form of the promoter was induced following phorbol 12-myristate 13-acetate treatment, while the −138C variant was refractive to phorbol 12-myristate 13-acetate treatment, confirming that AP-1 factors preferentially bind to the −138T variant. This study therefore suggests that a common polymorphism of the MGP promoter influences binding of the AP-1 complex, which may lead to altered transcription and serum levels. This could have important implications for diseases such as atherosclerosis and aortic valve stenosis, since it strongly suggests a genetic basis for regulation of tissue calcification.