Setzer D R, McGrogan M, Nunberg J H, Schimke R T
Cell. 1980 Nov;22(2 Pt 2):361-70. doi: 10.1016/0092-8674(80)90346-3.
We have examined in detail the RNA coding for dihydrofolate reductase (DHFR) in methotrexate-resistant mouse cells. We find four distinct DHFR messengers, ranging in size from 750 to 1600 nucleotides. All four are polyadenylated and polysomal and can be translated in vitro to produce a 21,000 dalton protein co-migrating with purified dihydrofolate reductase on SDS polyacrylamide gels. The major difference in these RNAs is the length of 3' untranslated regions, varying from about 80 nucleotides in the smallest mRNA to about 930 nucleotides in the largest. The RNAs are also present in methotrexate-sensitive murine cells and mouse liver. Multiple DHFR RNAs are found in the poly(A)+ RNA of methotrexate-resistant Chinese hamster ovary cells but are of different molecular weights than the mouse messengers. We discuss these results in terms of the function of 3' untranslated regions of eucaryotic mRNAs and the possible origin and significance of multiple messenger RNAs for a single protein.
我们已经详细研究了甲氨蝶呤抗性小鼠细胞中编码二氢叶酸还原酶（DHFR）的RNA。我们发现了四种不同的DHFR信使RNA，大小在750至1600个核苷酸之间。这四种信使RNA均为多聚腺苷酸化且存在于多核糖体中，并且可以在体外进行翻译，以产生一种21,000道尔顿的蛋白质，该蛋白质在SDS聚丙烯酰胺凝胶上与纯化的二氢叶酸还原酶共同迁移。这些RNA的主要差异在于3'非翻译区的长度，从最小的mRNA中的约80个核苷酸到最大的mRNA中的约930个核苷酸不等。这些RNA也存在于对甲氨蝶呤敏感的小鼠细胞和小鼠肝脏中。在甲氨蝶呤抗性中国仓鼠卵巢细胞的多聚腺苷酸（poly(A)+）RNA中发现了多种DHFR RNA，但它们的分子量与小鼠信使RNA不同。我们根据真核生物mRNA的3'非翻译区的功能以及单个蛋白质的多种信使RNA的可能起源和意义来讨论这些结果。
