Cadmium-induced differential accumulation of metallothionein isoforms in the Antarctic icefish, which exhibits no basal metallothionein protein but high endogenous mRNA levels

被引:53
作者
Carginale, V
Scudiero, R
Capasso, C
Capasso, A
Kille, P
di Prisco, G
Parisi, E
机构
[1] CNR, Ist Biochim Prot Enzimol, I-80125 Naples, Italy
[2] Univ Naples Federico II, Dipartimento Biol Evolut & Comparata, I-80100 Naples, Italy
[3] Univ Coll Wales, Sch Mol & Med Biosci, Cardiff CF1 3US, S Glam, Wales
关键词
D O I
10.1042/bj3320475
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
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.
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页码:475 / 481
页数:7
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