Reveillaud I, Lelay-Taha M N, Sri-Widada J, Brunel C, Jeanteur P
Mol Cell Biol. 1984 Sep;4(9):1890-9. doi: 10.1128/mcb.4.9.1890-1899.1984.
When U1 and U2 small nuclear ribonucleoproteins (snRNPs) purified by a procedure which preserves their immunoprecipitability by autoimmune antibodies (Hinterberger et al., J. Biol. Chem. 258:2604-2613, 1983), were submitted to extensive digestion with micrococcal nuclease, we found that their degradation pattern was sharply dependent upon magnesium concentration, indicating that they undergo a profound structural modification. At low Mg2+ (less than or equal to 5 mM), both particles only exhibit a core-resistant structure previously identified as being common to all but U6 snRNAs (Liautard et al., J. Mol. Biol. 162: 623-643, 1982). At high Mg2+ (greater than or equal to 7 mM), U1 and U2 snRNPs behave differently from one another. In U1 snRNP, most U1 snRNA sequence is protected, except for the 10 5'-terminal nucleotides presumably involved in splicing and a short sequence between nucleotides 102 and 108. Another region spanning nucleotides 60 to 79 is only weakly protected. This structural modification was demonstrated to be reversible. In U2 snRNP, the U2 snRNA sequence remains exposed in its 5' part up to nucleotide 92, and the 3'-terminal hairpin located outside the core structure becomes protected.
当通过一种能保持其被自身免疫抗体免疫沉淀能力的方法纯化的U1和U2小核核糖核蛋白（snRNP）（Hinterberger等人，《生物化学杂志》258:2604 - 2613，1983），用微球菌核酸酶进行广泛消化时，我们发现它们的降解模式强烈依赖于镁离子浓度，这表明它们经历了深刻的结构修饰。在低镁离子浓度（小于或等于5 mM）时，两种颗粒都只呈现出一种先前被确定为除U6 snRNA外所有snRNA共有的抗核心结构（Liautard等人，《分子生物学杂志》162: 623 - 643，1982）。在高镁离子浓度（大于或等于7 mM）时，U1和U2 snRNP的行为彼此不同。在U1 snRNP中，除了大概参与剪接的10个5'-末端核苷酸和核苷酸102与108之间的一小段序列外，大部分U1 snRNA序列受到保护。另一个跨越核苷酸60至79的区域仅受到微弱保护。这种结构修饰被证明是可逆的。在U2 snRNP中，U2 snRNA序列在其5'部分直至核苷酸92处仍暴露在外，并且位于核心结构之外的3'-末端发夹结构受到保护。
