Griffith J K
Mol Cell Biol. 1985 Dec;5(12):3525-31. doi: 10.1128/mcb.5.12.3525-3531.1985.
Recombinant DNA probes complementary to Chinese hamster metallothionein (MT)-1 and MT-2 mRNAs were used to compare MT gene copy numbers, zinc-induced MT mRNA levels, and uninduced MT mRNA levels in cadmium-resistant (Cdr) Chinese hamster ovary cell lines. Quantitative hybridization analyses determined that the MT-1 and MT-2 genes are each present at approximately single-copy levels in the genome of cell line Cdr2C10 and are coordinately amplified approximately 7, 3, and 12 times over the Cdr2C10 value in the genomes of cell lines Cdr20F4, Cdr30F9, and Cdr200T1, respectively. The maximum zinc-induced MT-1 mRNA concentrations in cell lines Cdr20F4, Cdr30F9, and Cdr200T1 were equal to 1, 3, and 15 times that measured in Cdr2C10, respectively. Similarly, the maximum zinc-induced MT-2 mRNA concentrations were equal to 1, 3, and 14 times that measured in Cdr2C10, respectively, and in each instance they were 90 to 150 times greater than their respective concentrations in uninduced cells. Thus, relative MT gene numbers are closely correlated with both zinc-induced and uninduced MT mRNA levels in Cdr2C10, Cdr30F9, and Cdr200T1, but not in Cdr20F4. Each of the latter two lines possesses structurally altered chromosomes whose breakpoints are near the MT locus. Nonetheless, the ratio of the levels of MT-1 to MT-2 mRNAs was constant in each of the four cell lines, including Cdr20F4. These results demonstrate that MT-1 and MT-2 mRNAs are induced coordinately in each Cdr cell line. Therefore, the coordination of the induction of MT-1 and MT-2 mRNA is independent of MT gene amplification, MT gene rearrangement, and the relative inducibilities of amplified MT genes. However, MT mRNA and protein levels each indicate that MT-1 and MT-2 expression is non-coordinate in uninduced cells. Thus, regulation of MT expression may involve two different mechanisms which are differentially operative in induced and uninduced cells.
利用与中国仓鼠金属硫蛋白（MT）-1和MT-2 mRNA互补的重组DNA探针，比较耐镉（Cdr）中国仓鼠卵巢细胞系中MT基因拷贝数、锌诱导的MT mRNA水平和未诱导的MT mRNA水平。定量杂交分析确定，在细胞系Cdr2C10的基因组中，MT-1和MT-2基因各自以大约单拷贝水平存在，并且在细胞系Cdr20F4、Cdr30F9和Cdr200T1的基因组中，它们分别比Cdr2C10值协调扩增了约7、3和12倍。细胞系Cdr20F4、Cdr30F9和Cdr200T1中最大的锌诱导MT-1 mRNA浓度分别等于在Cdr2C10中测得浓度的1、3和15倍。同样，最大的锌诱导MT-2 mRNA浓度分别等于在Cdr2C10中测得浓度的1、3和14倍，并且在每种情况下，它们比未诱导细胞中的各自浓度大90至150倍。因此，在Cdr2C10、Cdr30F9和Cdr200T1中，相对MT基因数与锌诱导的和未诱导的MT mRNA水平密切相关，但在Cdr20F4中并非如此。后两个细胞系中的每一个都具有结构改变的染色体，其断点靠近MT基因座。尽管如此，在包括Cdr20F4在内的四个细胞系中，MT-1与MT-2 mRNA水平的比率是恒定的。这些结果表明，在每个Cdr细胞系中，MT-1和MT-2 mRNA是协同诱导的。因此，MT-1和MT-2 mRNA诱导的协调性独立于MT基因扩增、MT基因重排以及扩增的MT基因的相对诱导能力。然而，MT mRNA和蛋白质水平均表明，在未诱导的细胞中，MT-1和MT-2的表达是不协同的。因此，MT表达的调控可能涉及两种不同的机制，它们在诱导细胞和未诱导细胞中发挥不同的作用。
