A doughnut-shaped heteromer of human Sm-like proteins binds to the 3′-end of U6 snRNA, thereby facilitating U4/U6 duplex formation in vitro
A doughnut-shaped heteromer of human Sm-like proteins binds to the 3′-end of U6 snRNA, thereby facilitating U4/U6 duplex formation in vitro
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DOI：
10.1093/emboj/18.20.5789
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发表时间：
1999-10-15
期刊：
影响因子：
11.4
通讯作者：
Lührmann, R
中科院分区：
文献类型：
--
作者：
Achsel, T;Brahms, H;Lührmann, R
我们描述了存在于人[U4/U6]中的七种不同蛋白的分离和分子特性。U5 tri-snRNPs。这些蛋白与Sm蛋白具有明显的同源性，因此被称为LSm （like Sm）蛋白。纯化后的LSm蛋白形成一种异聚体，即使在没有RNA的情况下也很稳定，在电子显微镜下呈现甜甜圈形状，与Sm核心RNP结构有着惊人的相似性。纯化的LSm异聚体特异性结合到U6 snRNA上，需要3'端u链才能形成复合物。用RNaseT消化分离的tri-snRNPs后，U6 snRNA的3'端也与LSm蛋白共沉淀(1)。重要的是，LSm蛋白不结合完整的U1， U2， U4或U5 snrna的U-rich Sm位点，表明它们只能与3'端U-tract相互作用。最后，我们发现LSm蛋白在体外促进U4/U6 RNA双链的形成，这表明LSm蛋白可能在U4/U6 snRNP的形成中发挥作用。
We describe the isolation and molecular characterization of seven distinct proteins present in human [U4/U6.U5] tri-snRNPs. These proteins exhibit clear homology to the Sm proteins and are thus denoted LSm (like Sm) proteins. Purified LSm proteins form a heteromer that is stable even in the absence of RNA and exhibits a doughnut shape under the electron microscope, with striking similarity to the Sm core RNP structure. The purified LSm heteromer binds specifically to U6 snRNA, requiring the 3'-terminal U-tract for complex formation. The 3'-end of U6 snRNA was also co-precipitated with LSm proteins after digestion of isolated tri-snRNPs with RNaseT(1). Importantly, the LSm proteins did not bind to the U-rich Sm sites of intact U1, U2, U4 or U5 snRNAs, indicating that they can only interact with a 3'-terminal U-tract. Finally, we show that the LSm proteins facilitate the formation of U4/U6 RNA duplices in vitro, suggesting that the LSm proteins may play a role in U4/U6 snRNP formation.