Evidence for differences in the post-transcriptional regulation of rat metallothionein isoforms.
The expression of metallothionein (MT)-1 and -2 mRNAs in rat liver following administration of Cd or Cu was investigated using specific oligonucleotides. The specificity was confirmed using a competitive prehybridization assay. Cd injection caused a biphasic induction of both isoform mRNAs, whereas Cu induced a sustained, monophasic response. Analysis of polyribosomal RNA showed that, after both Cd and Cu treatments, the recruitment of MT-1 mRNA into polyribosomes paralleled the increase in transcription, but the increase of polyribosomal MT-2 mRNA was less than that of total MT-2 mRNA. This indicates that not all the MT-2 mRNA induced was translated, suggesting that there is translational control of MT-2 mRNA expression, but not of MT-1 mRNA. This hypothesis was supported by the observation that, after Cu treatment, the induction of MT-1 protein was induced to the same extent as MT-1 mRNA, whereas the total MT protein (MT-1 + MT-2) was increased far less (7-fold) than MT-2 mRNA (30-fold).
Vasconcelos
M H
MH
Division of Biochemical Sciences, Rowett Research Institute, Aberdeen, Scotland, U.K.
Tam
S C
SC
Beattie
J H
JH
Hesketh
J E
JE
D000818:Animals; D001483:Base Sequence; D002104:Cadmium / Q000633:toxicity; D003300:Copper / Q000633:toxicity; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008668:Metallothionein / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats
D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D002104:Cadmium; D003300:Copper; D008668:Metallothionein