Abstract
Mitochondrial aconitase (mACON) contains a [4Feโ4S] cluster as the key enzyme for citrate oxidation in the human prostatic epithelial cell. Although there is accumulating evidence indicating that accumulation of high levels of zinc in prostate epithelial cells causes reduced efficiency of citrate oxidation, zinc regulation on the mACON is still not well understood. From in vitro studies, zinc chloride treatment has been developed using humic acid as the carrier (ZnโHA) in human prostatic carcinoma cells, PCโ3. ZnโHA treatment (0.1โ10 ฮผM) restricts mACON enzymatic activity, which attenuates citrate utility and decreases intracellular ATP levels in PCโ3 cells, whereas the effect is blocked by adding the zinc chelator, diethylenetriaminepentaacetic acid (DTPA). Immunoblot, ribonucleaseโprotection and transient geneโexpression assays indicate that ZnโHA treatments inhibit mACON gene expression. Mutation of the putative metal response element (MRE) from CTCGCCTTCA to TGATCCTTCA abolishes ZnโHA inhibition of mACON promoter activity. Our results have demonstrated that zinc possesses a specific regulatory mechanism on the mACON gene, and a biologic function of the putative metal regulatory system in mACON gene transcription has been identified. ยฉ 2005 WileyโLiss, Inc.