Heavy metal can have a profound deleterious effect on intracellular homeostasis and affect gene expression. It has been possible to correlate metals toxicity with carcinogenesis in various tissues. Metallothionein (MTs) are metal binding proteins and are thought to function in metal detoxification and metabolism. Mt gene transcription can be induced by metals. Metal activation of MT gene transcription is dependent on the presence of metal regulatory elements (MREs) shared by MT gene promoters and involves a trans-acting factor(s) interacting with the MRE. We have purified mouse MEP-1, a nuclear protein which binds with high affinity to MREs in a zinc-dependent manner. The carcinogenic effects of metals may be related to MT levels in the target organs. In humans, bladder cancer is related to environmental pollutants or as part of an altered tumor cell's complement of biochemical pathways. MT may also have a role in conferring resistance to cis-diamminedichloroplatinum (CDDP), an effective drug used in the treatment of advanced bladder carcinoma. This project is aimed at A) studying the mechanism by which metals activate MT gene expression, and B) assessing the expression of MT in human bladder tumors. This project aims specifically to: 1) Assess the transcriptional activity of MEP-1 in an in vitro transcription assay, clone mouse and human MEP-1 cDNAs and genes, map the functional domains of the protein and study MEP-1 expression in different tissues and cell lines. 2) Characterize the mouse homologues of the MRE-binding proteins. 3) Assess the role of the protein binding of the CAP site of the mMT-I gene in metal-regulated transcription and clone the corresponding cDNA. We have detected a nuclear protein binding to the CPA site of the mouse MT-I gene and thus the possible role of such a protein for metal- regulated MT gene transcription should be assessed. 4) Identify putative new tissue-specific MT gene family members in mouse liver, prostate, lung testes and characterize the regulatory elements of the mouse MT-III gene, a new MT gene which is noninducible by metals. 5) Assess MT expression in normal bladders and bladder tumors, and determine the isoform specificity of MT in these tissues. 6) Assess the value to MTs as cancer markers to predict the biological behavior of bladder tumors, and the response to CDDP-chemotherapy. The proposed studies should yield insight into the mechanisms governing metal-regulated MT gene transcription. The cloning of MEP-1-encoding cDNA may represent the first cloning of a metal-responsive transcription activation factor in metaxoans. These studies will also provide information on the expression of MT in staged human bladder tumors in patients having or not received CDDP therapy, thus contributing to defining the role of MT in bladder tumor progression and in the development of drug resistance.
| Faraonio, R; Moffatt, P; Larochelle, O et al. (2000) Characterization of cis-acting elements in the promoter of the mouse metallothionein-3 gene. Activation of gene expression during neuronal differentiation of P19 embryonal carcinoma cells. Eur J Biochem 267:1743-53 |
| Moffatt, P; Seguin, C (1998) Expression of the gene encoding metallothionein-3 in organs of the reproductive system. DNA Cell Biol 17:501-10 |
