A polymorphism of the human matrix gamma-carboxyglutamic acid protein promoter alters binding of an activating protein-1 complex and is associated with altered transcription and serum levels.
Matrix gamma-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.
Farzaneh-Far
A
A
Division of Cardiovascular Medicine, University of Cambridge, Addenbrooke's Hospital (ACCI level 6), Hills Road, Cambridge CB2 2QQ, United Kingdom. aff24@cam.ac.uk
Davies
J D
JD
Braam
L A
LA
Spronk
H M
HM
Proudfoot
D
D
Chan
S W
SW
O'Shaughnessy
K M
KM
Weissberg
P L
PL
Vermeer
C
C
Shanahan
C M
CM
D000818:Animals; D001011:Aorta; D001665:Binding Sites; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D011110:Polymorphism, Genetic; D018807:Polymorphism, Single-Stranded Conformational; D011401:Promoter Regions, Genetic; D051381:Rats; D017208:Rats, Wistar; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D000097568:Matrix Gla Protein
D002135:Calcium-Binding Proteins; D016326:Extracellular Matrix Proteins; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D013755:Tetradecanoylphorbol Acetate; D018808:Transcription Factor AP-1; D000097568:Matrix Gla Protein