Samarina O P, Peunova N I, Boĭsar D, Georgiev G P
Mol Biol (Mosk). 1979 Jan-Feb;13(1):60-72.
The nature of the 5'-termini in pre-mRNA isolated from Ehrlich carcinoma cells has been investigated. To discriminate between triphosphorylated 5'-ends and capped structures different methods were used including treatment by alkaline phosphatase and several chromatographic methods. It was shown that heavey pre-mRNA contains a significant number of non-blocked triphosphorylated nucleotides at the 5'-end termini. However, phosphatase resistent, blocked 5'-termini were also found. 5'-terminal nucleotides in triphosphorylated pre-mRNA are G in a 3 : 2 ratio. In contrast to nuclear pre-mRNA cytoplasmic poly(A)+mRNA does not contain triphosphorylated 5'-ends but does contain the "cap" structure only. To elucidate the pre-mRNA topography the localization of homopolymeric regions of pre-mRNA, poly(A) and oligo(U), in relation to 5'terminal structures has been investigated. The experiments showed that the distance between 3'-terminal poly(A) sequences and 5'-end triphosphates is longer than 1500--2000 nucleotides. At the same time the distance between the latter and oligo(U) in pre-mRNA is much shorter.
对从艾氏癌细胞中分离出的前体信使核糖核酸（pre-mRNA）5'-末端的性质进行了研究。为了区分三磷酸化的5'-末端和加帽结构，使用了不同的方法，包括碱性磷酸酶处理和几种色谱方法。结果表明，重链前体信使核糖核酸在5'-末端含有大量未封闭的三磷酸化核苷酸。然而，也发现了对磷酸酶有抗性的封闭5'-末端。三磷酸化前体信使核糖核酸中的5'-末端核苷酸以3:2的比例为鸟嘌呤（G）。与核内前体信使核糖核酸不同，细胞质多聚腺苷酸（poly(A)）+信使核糖核酸不含有三磷酸化的5'-末端，只含有“帽”结构。为了阐明前体信使核糖核酸的拓扑结构，研究了前体信使核糖核酸、多聚腺苷酸和寡聚尿苷酸（oligo(U)）的同聚物区域相对于5'-末端结构的定位。实验表明，3'-末端多聚腺苷酸序列与5'-末端三磷酸之间的距离超过1500 - 2000个核苷酸。同时，前体信使核糖核酸中后者与寡聚尿苷酸之间的距离要短得多。
