Suppression of HGF receptor gene expression by oxidative stress is mediated through the interplay between Sp1 and Egr-1.
Hepatocyte growth factor (HGF) receptor, the product of the c-met protooncogene, is transcriptionally regulated by a wide variety of cytokines as well as extracellular environmental cues. In this report, we demonstrate that c-met expression was significantly suppressed by oxidative stress. Treatment of mouse renal inner medullary collecting duct epithelial cells with 0.5 mM H(2)O(2) inhibited c-met mRNA and protein expression, which was concomitant with induction of Egr-1 transcription factor. Ectopic expression of Egr-1 in renal epithelial cells markedly inhibited endogenous c-met expression in a dose-dependent fashion, suggesting a causative effect of Egr-1 in mediating c-met suppression. The cis-acting element responsible for H(2)O(2)-induced c-met inhibition was localized at nucleotide position -223 to -68 of c-met promoter, in which reside an imperfect Egr-1 and three Sp1-binding sites. Egr-1 markedly suppressed c-met promoter activity but did not directly bind to its cis-acting element in the c-met gene. Induction of Egr-1 by oxidative stress attenuated the binding of Sp1 to its cognate sites, but it did not affect Sp1 abundance in renal epithelial cells. Immunoprecipitation uncovered that Egr-1 physically interacted with Sp1 by forming the Sp1/Egr-1 complex, which presumably resulted in a decreased availability of unbound Sp1 as a transcriptional activator for the c-met gene. Thus it appears that inhibition of c-met expression by oxidative stress is mediated by the interplay between Sp1 and Egr-1 transcription factors. Our findings reveal a novel transcriptional regulatory mechanism by which Egr-1 sequesters Sp1 as a transcriptional activator of c-met via physical interaction.
Zhang
Xianghong
X
Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
Liu
Youhua
Y
D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000502:physiology*; D051766:Early Growth Response Protein 1; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation / Q000502:physiology*; D017874:Immediate-Early Proteins; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D008156:Luciferases / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D018384:Oxidative Stress / Q000502:physiology*; D010957:Plasmids; D011233:Precipitin Tests; D019859:Proto-Oncogene Proteins c-met / Q000096:biosynthesis* / Q000235:genetics; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D014157:Transcription Factors / Q000502:physiology*; D014162:Transfection
D004268:DNA-Binding Proteins; D051766:Early Growth Response Protein 1; C486109:Egr1 protein, mouse; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D012313:RNA; D004247:DNA; D008156:Luciferases; D019859:Proto-Oncogene Proteins c-met