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(356) ZINC REGULATES THE PUTATIVE METAL-RESPONSE ELEMENT OF HUMAN MITOCHONDRIAL ACONITASE GENE IN THE HUMAN PROSTATE CARCINOMA CELLS. Juang, Horng-Heng1, 1 Dept of Anatomy, Tao-Yuan, Taiwan ABSTRACT- The mitochondrial aconitase (mACON) is an enzyme containing a [4Fe-4S] cluster as the key enzyme for citrate oxidation in human prostate epithelial cell. In vitro study using the human prostate carcinoma cells, PC-3 cells, we demonstrates that zinc chloride (Zn) treatments (0.01 mM) using the humic acid as the carrier for 16 hours significantly inhibit mACON enzymatic activity and this Zn effect is blocked by cotreated with the zinc chelator, DTPA. Zn inhibits mACON enzymatic activity which attenuates intracellular ATP biosynthesis but stimulates citrate secretion in PC-3 cells. Immunoblotting assay suggests that Zn blocks mACON protein biosynthesis. Reporter assay using the luciferase report vector (pGL2) containing the putative iron response element (IRE) and metal response element (MRE) in the promoter-frankling region of human mACON gene demonstrates that Zn inhibits human mACON gene transcription. Mutation of MRE from CTCGCCTTC to CTGATCCTTC using the method of site-directed mutagenesis abolished the repressing effects of Zn. Mutation assays indicate that Zn effects on the human mACON gene through the MRE but not the IRE pathway. Our results demonstrate that Zn and Fe has different regulatory mechanism on the mACON gene and identify a biologic function of the putative mental regulatory system in mACON gene transcription. KEY WORDS: aconitase, citrate, prostate, zinc |
