Identification of two Sp1 phosphorylation sites for p42/p44 mitogen-activated protein kinases: their implication in vascular endothelial growth factor gene transcription.
Sp1 regulates activation of many genes implicated in tumor growth and cell cycle progression. We have previously demonstrated its implication in the up-regulation of vascular endothelial growth factor (VEGF) gene transcription following growth factor stimulation of quiescent cells, a situation where p42/p44 mitogen-activate protein kinase (MAPK) activity is dramatically increased. Here we show that p42/p44 MAPK directly phosphorylates Sp1 on threonines 453 and 739 both in vitro and in vivo. Mutation of these sites to alanines decreases by half the MAPK-dependent transcriptional activity of Sp1, in the context of the VEGF promoter, in SL2 Drosophila cells devoid of the endogenous Sp1 protein. Moreover, inducible overexpression of the (T453A,T739A) Sp1 double mutant compromises MAPK-driven VEGF mRNA transcription in fibroblasts. These results highlight Sp1 as a key molecular link between elevated activation of the Ras >> p42/p44MAPK signaling pathway and increased VEGF expression, two major steps deregulated in tumor cells.
Milanini-Mongiat
Julie
J
Institute of Signalling, Developmental Biology and Cancer Research, Centre Antoine Lacassagne, 33 avenue de Valombrose, 06189 Nice cedex 2, France.
Pouysségur
Jacques
J
Pagès
Gilles
G
D001483:Base Sequence; D017931:DNA Primers; D016228:Endothelial Growth Factors / Q000235:genetics*; D008222:Lymphokines / Q000235:genetics*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D018919:Neovascularization, Physiologic / Q000235:genetics; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics; D016329:Sp1 Transcription Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D017931:DNA Primers; D016228:Endothelial Growth Factors; D008222:Lymphokines; D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases