CLK1 reorganizes the splicing factor U1-70K for early spliceosomal protein assembly
CLK1 reorganizes the splicing factor U1-70K for early spliceosomal protein assembly
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DOI：
10.1073/pnas.2018251118
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发表时间：
2021-04-06
影响因子：
11.1
通讯作者：
Adams, Joseph A.
中科院分区：
文献类型：
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作者：
Aubol, Brandon E.;Wozniak, Jacob M.;Adams, Joseph A.
早期剪接体组装需要U1-70K的磷酸化，U1是U1小核核糖核蛋白(SnRNP)的组成部分，但尚不清楚哪些位点被磷酸化，由什么酶作用，以及这种修饰如何调节功能。通过对蛋白质组的分析，我们发现CDC2样激酶1(CLK1)在U1-70K的C末端磷酸化Ser-226。这将从亚核颗粒中释放U1-70K，促进与U1 SnRNP和丝氨酸-精氨酸(SR)蛋白SRSF1的相互作用，这是建立5‘剪接位点的关键步骤。CLK1切断了U1-70K中C末端与RNA识别基序(RRM)之间的联系，释放了RRM与SRSF1结合。这种重组也允许U1-70K与几种与U1 SnRNP相关的蛋白质之间稳定的相互作用。SR蛋白激酶1(SRPK1)的核诱导促进CLK1从U1-70K解离，使其循环用于催化。这些研究表明，CLK1通过绘制U1-70K的轮廓来进行蛋白质-蛋白质多任务，在早期剪接体蛋白质组装中发挥着重要的信号依赖作用。
Early spliceosome assembly requires phosphorylation of U1-70K, a constituent of the U1 small nuclear ribonucleoprotein (snRNP), but it is unclear which sites are phosphorylated, and by what enzyme, and how such modification regulates function. By profiling the proteome, we found that the Cdc2-like kinase 1 (CLK1) phosphorylates Ser-226 in the C terminus of U1-70K. This releases U1-70K from subnuclear granules facilitating interaction with U1 snRNP and the serine-arginine (SR) protein SRSF1, critical steps in establishing the 5' splice site. CLK1 breaks contacts between the C terminus and the RNA recognition motif (RRM) in U1-70K releasing the RRM to bind SRSF1. This reorganization also permits stable interactions between U1-70K and several proteins associated with U1 snRNP. Nuclear induction of the SR protein kinase 1 (SRPK1) facilitates CLK1 dissociation from U1-70K, recycling the kinase for catalysis. These studies demonstrate that CLK1 plays a vital, signal-dependent role in early spliceosomal protein assembly by contouring U1-70K for protein-protein multitasking.