The role of MTF-1 in regulating zebrafish hemopexin gene expression. A) Schematic of the region of the proximal zebrafish hemopexin gene promoter containing putative MRE motifs cloned into the pGL4.10[luc2] vector (Promega Corporation, Madison, WI). B and C) In transient transfection assays, Hepa1c1c7 cells were transfected with 40 ng of zfHpx-Luc, 20 ng of zebrafish MTF-1 and 60 ng of dnMTF-1. The zfHpx-Luc construct was responsive to Zn but not Cd treatment. Addition of exogenous MTF-1, but not dnMTF-1, inhibited the Zn-induced increase in luciferase activity. Co-transfection of dnMTF-1 rescued the inhibition of zfHpx-Luc activation by MTF-1. Error bars represent one standard deviation: n = 6 replicates. The results shown are representative of two independent experiments.