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  • Title: [Structure of nuclear pre-mRNA. XI. Triphosphorylated and blocked 5'-ends in the pre-mRNA].
    Author: Samarina OP, Peunova NI, Boĭsar D, Georgiev GP.
    Journal: Mol Biol (Mosk); 1979; 13(1):60-72. PubMed ID: 460197.
    Abstract:
    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.
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