Hypoxia acts through multiple signaling pathways to induce metallothionein transactivation by the metal-responsive transcription factor-1 (MTF-1)

Abstract

Metal-responsive transcription factor-1 (MTF-1) is essential for the induction of genes encoding metallothionein by metals and hypoxia. Here, we studied the mechanism controlling the activation of MTF-1 by hypoxia. Hypoxia activation of Mt gene transcription is dependent on the presence of metal regulatory elements (MREs) in the promoter of Mt genes. We showed that MREa and MREd are the main elements controlling mouse Mt-1 gene induction by hypoxia. Transfection experiments in Mtf-1-null cells showed that MTF-1 is essential for induction by hypoxia. Chromatin immunoprecipitation analysis showed that MTF-1 DNA-binding activity was strongly enhanced in the presence of zinc but not by hypoxia. Notably, hypoxia inducible factor- (HIF) 1α was recruited to the Mt-1 promoter in response to hypoxia but not to zinc. MTF-1 activation was inhibited by PKC, JNK, and PI3K inhibitors and by the electron transport chain inhibitors rotenone and myxothiazol, but not by the antioxidant N-acetylcysteine. We showed that prolyl-hydroxylase inhibitors can activate MTF-1, but this activation requires the presence of HIF-1α. Finally, HIF-dependent transcription is enhanced in the presence of MTF-1 and induction of an MRE promoter is stimulated by HIF-1α, thus indicating cooperation between these 2 factors. However, coimmunoprecipitation experiments did not suggest direct interaction between MTF-1 and HIF-1α.

Possible mechanisms underlying transcriptional induction of metallothionein isoforms by tris(pentafluorophenyl)stibane, tris(pentafluorophenyl)arsane, and tris(pentafluorophenyl)phosphane in cultured bovine aortic endothelial cells

“…Previously, we reported that P35 as well as Sb35 and As35 induce the expression of endothelial MT-2A by activating MRE (Fujie et al, 2016c). Therefore, our present and previous data suggest that Sb35 and As35 activate MTF-1, leading to the activation of MREs in the promoter region of MT, whereas P35 also activates the MREs by transcriptional factor(s) other than MTF-1 such as hypoxia inducible factor-1α (Dubé et al, 2011). As a result, these organopnictogen compounds induce the expression of MT-2A in vascular endothelial cells.…”

The phosphoinositide 3-kinase pathway and glycogen synthase kinase-3 positively regulate the activity of metal-responsive transcription factor-1 in response to zinc ions

“…The LUC reporter plasmid MT1-LUC contains 1843 bp of the 5= flanking region and 68 bp of the 5= untranslated region from the mouse Mt1 gene (Faraonio et al 2000). Similarly, the plasmid MT2A-LUC contains a human Mt2A gene DNA fragment (positions -780 to +65) cloned into pGL2 basic (Promega, Madison, Wisconsin, USA) (Dubé et al 2011). To construct plasmid (MREd) 6 -LUC, a synthetic DNA fragment containing 6 mouse Mt1 MREd elements (Labbé et al 1991) (5 elements in direct tandem orientation and the 6th in the opposite orientation) was cloned in front of a minimal mouse Mt1 promoter DNA fragment (positions -35 to -68) into the LUC reporter plasmid pGL2-Basic (Promega, Madison, Wis.).…”

Molecular cloning of metal-responsive transcription factor-1 (MTF-1) and transcriptional responses to metal and heat stresses in Pacific abalone, Haliotis discus hannai

“…Metal exposures were done with cadmium or zinc with the dose strengths of 20 and 100 ppb for 24 h. RT-qPCR data were presented as fold changes of MTF-1 mRNAs in expressed groups relative to that of non-exposed control (Con) based on the normalization against two internal control genes (RPL5 and PPL7). Histograms with different letters indicate the significantly different means based on ANOVA followed by Duncan's multiple ranged tests at P < 0.05 (Dubé et al 2011;Cheuk et al 2008) and carp (Ferencz and Hermesz 2009), which is obviously different from the principle for the MTF-1 regulation in mammals (Bi et al 2006;Saydam et al 2001).…”

“…Besides, several transcription factor binding sites such as heat shock element (HSE; GAANRTTC; −1003 and −32 bp; targeted by heat shock factor (HSF)), hypoxia response element (HRE; RCGTG; −895 and −285 bp; by hypoxiainducible factor-1 alpha (HIF-1α)), and other sites recognized by cyclic AMP response element binding protein (CREBP; TGACGY; −1253 bp) and nuclear factor for activated T-cells (NF-AT1; WGGAAA; −941, −169, and −33 bp) were predicted. All of these factors have been known to be related with stress responses of animals (Saydam et al 2003;Dubé et al 2011). Abalone MTF-1 promoter also revealed motifs that might be targeted by transcription factors generally known to be involved in development, signal transduction, cell proliferation and/or organ development.…”