The carboxyl-terminal cysteine residues of MTF1 are critical for arsenic sensing and induction of MT1.
Toxicologist 2010 Mar; 114(1):386
Metal-activated transcription factor 1 (MTF1) mediates the induction of metal-lothioneins (MT) I and II by zinc and stress signals. The mechanism of MTF1 activation has not been well understood. We analyzed the interaction between arsenic (As) and MTF1 for Mt1 induction. As potently induces Mt1 mRNA expression in mouse hepa1c1c7 cells. Induction is dependent upon functional MTF1 as induction is lost in Mtf1 knockout (KO) cells but is restored upon reconstitution with Mtf1; Moreover, As induces the binding of MTF1 to the metal response elements of endogenous Mt1. Induction is not affected by modulating zinc concentrations but is markedly enhanced by cycloheximide. Phenylarsine oxide (PAO) that covalently binds to vicinal protein cysteine thiol groups induces Mt1 with a magnitude of higher potency than that of As. PAO affinity beads effectively pulls down the carboxyl half of MTF1 (MTF1 321-675) by binding to a cluster of five cysteine residues near the terminus. Preincubation with As, Cd, Co, Ni, Ag, Hg, and Bi blocks pull-down of MTF1 321-675 by PAO beads in vitro and in vivo, indicating binding of the metal inducers to the same C-terminal cysteine cluster as PAO. Deletion of the C-terminal cysteine cluster or mutation of the cysteine residues abolishes or markedly reduces the transcription activation activity of MTF1 and the ability of MTF1 to restore Mt1 induction in Mtf1 KO cells. The findings demonstrate a critical role of the C-terminal cysteine cluster of MTF1 in arsenic sensing and gene transcription via arsenic-cysteine thiol interaction.
Biological-effects; Cell-biology; Cell-differentiation; Cell-function; Cellular-function; Cellular-reactions; Exposure-assessment; Genotoxic-effects; Genotoxicity; Gene-mutation; Genes
The Toxicologist. Society of Toxicology 49th Annual Meeting and ToxExpo, March 7-11, 2010, Salt Lake City, Utah