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.
Rafty
L A
LA
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.
Khachigian
L M
LM
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