FIG. 5.

Inhibition of nuclear export does not abolish metal inducibility. (A) MTF-1 null cells (dko7) were transfected with a reporter plasmid under the control of four tandem MREs, a reference plasmid, and hMTF-1-VSV. Thirty-six hours after transfection cells were treated with either LMB or solvent alone or left untreated. After 2 h, zinc sulfate (final concentration, 100 μM) was added to the cells as indicated (while LMB remained present). RNA was isolated from the cells and quantified by an S1 nuclease protection assay. Export inhibition by LMB treatment does not abolish induction by zinc (center). Error bars indicate the standard deviations of data from three independent experiments. EtOH, ethyl alcohol; rel., relative. (B and C) To test whether export inhibition by LMB was efficient, MTF-1 null cells (dko7) were transfected and treated with zinc or LMB as described above, and the subcellular localization of MTF-1-VSV was analyzed by anti-VSV immunofluorescent staining. For quantification, 200 cells each were counted and classified into the indicated categories (c, cytoplasm; n, nucleus). FITC, fluorescein isothiocyanate; nt, not treated.