Chan Shih-Peng, Kao Der-I, Tsai Wei-Yü, Cheng Soo-Chen
Institute of Microbiology and Immunology, National Yang-Ming University, Shih-Pai, Taiwan, Republic of China.
Science. 2003 Oct 10;302(5643):279-82. doi: 10.1126/science.1086602. Epub 2003 Sep 11.
During spliceosome activation, a large structural rearrangement occurs that involves the release of two small nuclear RNAs, U1 and U4, and the addition of a protein complex associated with Prp19p. We show here that the Prp19p-associated complex is required for stable association of U5 and U6 with the spliceosome after U4 is dissociated. Ultraviolet crosslinking analysis revealed the existence of two modes of base pairing between U6 and the 5' splice site, as well as a switch of such base pairing from one to the other that required the Prp19p-associated complex during spliceosome activation. Moreover, a Prp19p-dependent structural change in U6 small nuclear ribonucleoprotein particles was detected that involves destabilization of Sm-like (Lsm) proteins to bring about interactions between the Lsm binding site of U6 and the intron sequence near the 5' splice site, indicating dynamic association of Lsm with U6 and a direct role of Lsm proteins in activation of the spliceosome.
在剪接体激活过程中，会发生大规模的结构重排，其中涉及两个小核RNA（U1和U4）的释放，以及与Prp19p相关的蛋白质复合物的添加。我们在此表明，在U4解离后，与Prp19p相关的复合物对于U5和U6与剪接体的稳定结合是必需的。紫外线交联分析揭示了U6与5'剪接位点之间存在两种碱基配对模式，并且在剪接体激活过程中，这种碱基配对会从一种模式转换为另一种模式，而这需要与Prp19p相关的复合物。此外，还检测到U6小核核糖核蛋白颗粒中存在一种依赖于Prp19p的结构变化，该变化涉及Sm样（Lsm）蛋白的不稳定，从而导致U6的Lsm结合位点与5'剪接位点附近的内含子序列之间发生相互作用，这表明Lsm与U6存在动态结合，并且Lsm蛋白在剪接体激活中起直接作用。
