Abstract
Metal-responsive transcription factor 1 (MTF-1) is an essential mammalian protein for embryonic development and modulates the expression of genes involving in Zn homeostasis and responding to oxidative stress. We report here that phosphatase and tensin homologue deleted on chromosome 10 (PTEN) associates with MTF-1 in the cells. These two proteins interact via the acidic domain of MTF-1 and the phosphatase/C2 domain of PTEN. Depletion of PTEN reduced metallothionein (MT) gene expression and increased cellular sensitivity to cadmium toxicity. PTEN did not alter the nuclear translocation, protein stability or DNA-binding activity of MTF-1 and cellular absorption of metal ions. Zn increased MTF-1/PTEN interaction in a dose-dependent manner. The interaction elevated within 2 h of Zn addition and declined afterward in the cells. The enhanced binding activity occurred mainly in cytoplasm and reduced after translocating the MTF-1 into nucleus. In addition, PTEN had not been recruited in MT promoter upon Zinc exposure. Blocking signalling through the phosphatidylinositol 3-kinase pathway did not alter the Zn-induced MT expression. Analysis of enzymatically inactive PTEN mutants demonstrated that protein but not lipid phosphatase activity of PTEN was involved in the regulation of MTF-1 activity. Elevation of PTEN expression reduced the phosphorylation level of MTF-1 as recognized by anti-phosphotyrosine antibody. The same regulatory role of PTEN was also noted in the regulation of Zn transporter 1, another target gene of MTF-1. Our results reveal a novel mode of regulation for MTF-1.