KUGE Shusuke Tohoku University, Graduate School of Pharmaceutical Sciences, Associate Professor, 大学院・薬学研究科, 助教授 (50186376)
MIYAIRI Shinichi Nihon University, School of Pharmaceutical Sciences, Professor, 薬学部, 教授 (50209855)
三浦 伸彦 独立行政法人産業医学総合研究所, 研究員 (20229644)
|Budget Amount *help
¥13,900,000 (Direct Cost: ¥13,900,000)
Fiscal Year 2002: ¥6,700,000 (Direct Cost: ¥6,700,000)
Fiscal Year 2001: ¥7,200,000 (Direct Cost: ¥7,200,000)
Metallothionein (MT), the synthesis of which is induced by heavy metals such as cadmium (Cd), binds tightly with these heavy metals and suppress their toxicity. In healthy people, Cd mainly accumulates in the kidney, which is the primary target of Cd toxicity, and is present as MT-bound non-toxic forms. However, the possibility of the presence of a group of people with abnormalities of MT synthesis (high-risk group) cannot be excluded. In this study, therefore, we directed attention to gene mutations as possible causes of abnormal MT synthesis, and evaluated the relationship between abnormal base sequences in the promoter region of MT gene and MT synthesis. When we examined mutations of the promoter region using DNA isolated from white blood cells of 119 healthy Japanese people by the SSCP method, only the one-base substitution from adenine (A) to guanine (G) at the 5th base upstream (-5) of the starting point of transcription (+1), which we detected before, was observed again. Concerning the frequency of its occurrence, the homozygote of adenine, which is the wild type, was observed in 98 subjects (82.4%), heterozygotes of adenine and guanine were observed in 20(16.8%), and the homozygote of guanine was observed in 1(0.8%). This mutant site was present in the core promoter region between TATA box and the starting point of transcription, and the mutant promoter (-5G) had significantly less transcription activating efficiency by Zn and Cd than the wild type (-5A). We also evaluated a simple method for identification of people with a mutation in the promoter and established the fragment length measurement method based on the disappearance of the site that is cut by the restriction enzyme BsgI due to mutation. This identification of a high-risk group for Cd toxicity by this method may allow early prevention of Cd poisoning.