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Fibroblast Growth Factor-2 Represses Platelet-derived Growth Factor Receptor-α (PDGRD-α) Transcription via ER1/2-dependent Sp1 Phosphorylation and an Atypical cis-Acting Element in the Proximal PDGFR-α Promoter.

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Title: Fibroblast Growth Factor-2 Represses Platelet-derived Growth Factor Receptor-α (PDGRD-α) Transcription via ER1/2-dependent Sp1 Phosphorylation and an Atypical cis-Acting Element in the Proximal PDGFR-α Promoter.
Authors: Bonello, Michell R.1, Khachigian, Levon M.1 L.Khachigian@unsw.edu.Au
Source: Journal of Biological Chemistry. 1/23/2004, Vol. 279 Issue 4, p2377-2382. 6p. 13 Graphs.
Subjects: Growth factors, Blood platelets, Fibroblast growth factors, Genetic transcription, Phosphorylation, Smooth muscle, Muscle cells
Abstract: Platelet-derived growth factor (PDGF) is a potent mitogen and chemoattractant for vascular smooth muscle cells (SMCs) whose biological activity is mediated via its high affinity interaction with specific cell surface receptors. The molecular mechanisms governing the expression of PDGF receptor-α (PDGFR-α) are poorly understood. Here we demonstrate that PDGFR-α protein and transcriptional regulation in SMCs is under the positive regulatory influence of the zinc finger nuclear protein, Sp1. Electrophoretic mobility shift, competition, and supershift analysis revealed the existence of an atypical G-rich Sp1-binding element located in the PDGFR-α promoter -61 to -52 bp upstream of the transcriptional start site. Mutation of this sequence ablated endogenous Sp1 binding and activation of the PDGFR-α promoter. PDGFR-α transcription, mRNA, and protein expression were repressed in SMCs exposed to fibroblast growth factor-2 (FGF-2). This inhibition was rescued by the blockade of extracellular signal.regulated kinase-1/2 (ERK1/2). FGF-2 repression of PDGFR-α transcription was abrogated upon mutation of this Spl-response element. FGF-2 stimulated Sp1 phosphorylation in an ERK1/2 but not p38-dependent manner, the growth factor enhancing Spl interaction with the PDGFR-α promoter. Mutation of residues Thr[sup 453] and Thr[sup 739] in Sp1 (amino acids phosphorylated by ERK) blocked FGF-2 repression of PDGFR-α transcription. These findings, taken together, demonstrate that FGF-2 stimulates ERK1/2-dependent Sp1 phosphorylation, thereby repressing PDGFR-α transcription via the -61/-52 element in the PDGFR-α promoter. Phosphorylation triggered by FGF-2 switches Sp1 from an activator to a repressor of PDGFR-α transcription, a finding previously unreported in any Sp1-dependent gene. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Platelet-derived growth factor (PDGF) is a potent mitogen and chemoattractant for vascular smooth muscle cells (SMCs) whose biological activity is mediated via its high affinity interaction with specific cell surface receptors. The molecular mechanisms governing the expression of PDGF receptor-α (PDGFR-α) are poorly understood. Here we demonstrate that PDGFR-α protein and transcriptional regulation in SMCs is under the positive regulatory influence of the zinc finger nuclear protein, Sp1. Electrophoretic mobility shift, competition, and supershift analysis revealed the existence of an atypical G-rich Sp1-binding element located in the PDGFR-α promoter -61 to -52 bp upstream of the transcriptional start site. Mutation of this sequence ablated endogenous Sp1 binding and activation of the PDGFR-α promoter. PDGFR-α transcription, mRNA, and protein expression were repressed in SMCs exposed to fibroblast growth factor-2 (FGF-2). This inhibition was rescued by the blockade of extracellular signal.regulated kinase-1/2 (ERK1/2). FGF-2 repression of PDGFR-α transcription was abrogated upon mutation of this Spl-response element. FGF-2 stimulated Sp1 phosphorylation in an ERK1/2 but not p38-dependent manner, the growth factor enhancing Spl interaction with the PDGFR-α promoter. Mutation of residues Thr[sup 453] and Thr[sup 739] in Sp1 (amino acids phosphorylated by ERK) blocked FGF-2 repression of PDGFR-α transcription. These findings, taken together, demonstrate that FGF-2 stimulates ERK1/2-dependent Sp1 phosphorylation, thereby repressing PDGFR-α transcription via the -61/-52 element in the PDGFR-α promoter. Phosphorylation triggered by FGF-2 switches Sp1 from an activator to a repressor of PDGFR-α transcription, a finding previously unreported in any Sp1-dependent gene. [ABSTRACT FROM AUTHOR]
ISSN:00219258
DOI:10.1074/jbc.M308254200