Cadmium-induced differential accumulation of metallothionein isoforms in the Antarctic icefish, which exhibits no basal metallothionein protein but high endogenous mRNA levels
Cadmium-induced differential accumulation of metallothionein isoforms in the Antarctic icefish, which exhibits no basal metallothionein protein but high endogenous mRNA levels
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DOI：
10.1042/bj3320475
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发表时间：
1998-06-01
影响因子：
4.1
通讯作者：
Parisi, E
中科院分区：
文献类型：
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作者：
Carginale, V;Scudiero, R;Parisi, E
利用逆转录酶介导的PCR技术从银鱼肝脏中提取的RNA中分离出两种不同的金属硫蛋白（MT）cDNA，即MT-Ⅰ和MT-Ⅱ。这些cDNA的北方印迹分析表明，显着的内源性水平的MT mRNA存在于正常动物的肝组织中，尽管事实上，没有MT蛋白可以发现在同一组织中积累。然而，多次注射氯化镉诱导高水平的MT mRNA和MT蛋白。镉注射后存在的cDNA物种的序列分析显示，存在两种亚型，MT-I和MT-II转录正常和重金属处理的鱼的定量显示MT亚型转录的比例的改变。内源性成绩单主要由MT-II，而MT-I成绩单优先积累只在响应镉盐。从重金属处理的鱼中分离出由每个cDNA亚型编码的蛋白质，并通过体外翻译证明了用于翻译的特定MT mRNA的可用性。这些结果表明：结果表明：（1）银鱼肝脏MT mRNA的内源表达水平与MT蛋白的缺失之间存在差异;（2）重金属可诱导MT在银鱼肝脏中的积累;（3）不同MT亚型的基因受重金属的不同调控。
Reverse transcriptase-mediated PCR has been used to isolate two distinct metallothionein (MT) cDNA species from RNA extracted from icefish liver, namely MT-I and MT-II. Northern blot analysis with these cDNA species revealed that significant endogenous levels of MT mRNA were present in liver tissues of normal animals despite the fact that no MT protein could be found accumulating in the same tissue. However, multiple injections of CdCl2 induced high levels of both MT mRNA and MT protein. Sequence analysis of the cDNA species that were present after cadmium injection revealed the presence of both isoforms, Quantification of the MT-I and MT-II transcripts from normal and heavy-metal-treated fish showed an alteration in the ratio of the MT isoform transcripts. Endogenous transcripts consisted mostly of MT-II, whereas the MT-I transcript was preferentially accumulated only in response to the cadmium salt. The protein encoded by each cDNA isoform was isolated from the heavy-metal-treated fish and the availability of the specific MT mRNA for translation was demonstrated by translation in vitro. These results show that: (1) there is a discrepancy between the significant endogenous levels of MT mRNA and the absence of MT protein; (2) the accumulation of MT in icefish liver can be triggered by heavy metals; (3) genes encoding distinct MT isoforms are differentially regulated by heavy metals.