Suppression of HGF receptor gene expression by oxidative stress is mediated through the interplay between Sp1 and Egr-1

Abstract

Hepatocyte growth factor (HGF) receptor, the product of the c-metprotooncogene, 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 H2O2inhibited 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 H2O2-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.

Zinc Protoporphyrin Regulates Cyclin D1 Expression Independent of Heme Oxygenase Inhibition

“…By altering the interplay between Sp1 and Egr1, ZnPP could provide a means to manipulate gene expression relevant to tumorigenesis. Consistent with this hypothesis, gene expression of Met and Flt-1, all regulated by the interplay between Sp1 and Egr1 on the S/E site (40,47), are also inhibited by ZnPP in this study.…”

“…Decreased Sp1 or enhanced Egr1 binding could lead to either transcriptional activation or repression, respectively. For example, Egr1 acts as a negative regulator and represses Sp1-mediated activation of some genes including protein-tyrosine phosphatase 1B, Met, Epstein-Barr virus C, and ␤ 1 -adrenergic receptor (40,42,44,45). In another circumstance, Egr1 competes with Sp1 protein for an overlapping region in the promoter of platelet-derived growth factor A and functions as a positive activator (46).…”

The disturbance of oxidant-antioxidant balance in rat colonic mucosa after antibiotic therapy

“…A protective role of Sp-1 was found during oxidative stress in brain neurons [9,14]. The regulation of gene expression by Egr-1 and Sp-1 transcription factors showed an interaction between them, since DNA-binding domains of these factors overlap [14,17]. We [14], and others [4,16], showed that Egr-1 and Sp-1 play an important role in pathogenesis of the inflammatory bowel diseases.…”

Expression of NAG-1, a Transforming Growth Factor-β Superfamily Member, by Troglitazone Requires the Early Growth Response Gene EGR-1

“…5A, cotransfection of EGR-1 increased NAG-1 promoter activity after TGZ treatment, whereas Sp1 expression resulted in the reduction of NAG-1 promoter activity compared with empty vector transfection. Functional interplay between Sp1 and EGR-1 has been described for a number of human gene promoters (49,(52)(53)(54). The cis-acting element required for Sp1/EGR-1 binding is usually represented by a GC-rich sequence (GC box).…”