Sp1 phosphorylation regulates inducible expression of platelet-derived growth factor B-chain gene via atypical protein kinase C-zeta.
Platelet-derived growth factor (PDGF) is a broadly expressed mitogenic and chemotactic factor with diverse roles in a number of physiologic and pathologic settings. The zinc finger transcription factors Sp1, Sp3 and Egr-1 bind to overlapping elements in the proximal PDGF B-chain promoter and activate transcription of this gene. The anthracycline nogalamycin has previously been reported to inhibit the capacity of Egr-1 to bind DNA in vitro. Here we used electrophoretic mobility shift assays to show that nogalamycin added to cells in culture did not alter the interaction of Egr-1 with the PDGF-B promoter. Instead, it enhanced the capacity of Sp1 to bind DNA. Nogalamycin increased PDGF-B mRNA expression at the level of transcription, which was abrogated by mutation of the Sp1 binding site in the PDGF-B promoter or overexpression of mutant Sp1. Rather than increasing total levels of Sp1, nogalamycin altered the phosphorylation state of the transcription factor. Overexpression of dominant-negative PKC-zeta blocked nogalamycin-inducible Sp1 phosphorylation and PDGF-B promoter-dependent expression. Nogalamycin stimulated the phosphorylation of PKC-zeta (on residue Thr(410)). These findings demonstrate for the first time that PKC-zeta and Sp1 phosphorylation mediate the inducible expression of this growth factor.
Department of Haematology, The Prince of Wales Hospital and Centre for Thrombosis and Vascular Research, School of Pathology, The University of New South Wales, Sydney, NSW 2052, Australia.
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Rafty
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Khachigian
D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009621:Nogalamycin / Q000494:pharmacology; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D013997:Time Factors; D016335:Zinc Fingers / Q000235:genetics; D000099221:Protein Kinase C zeta
D015500:Chloramphenicol O-Acetyltransferase; D004247:DNA; D009621:Nogalamycin; D009841:Oligonucleotides; D010982:Platelet-Derived Growth Factor; D011493:Protein Kinase C; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; D000099221:Protein Kinase C zeta