Sad1 拮抗 Brr2 介导的 U4/U6.U5 在三 snRNP 动态平衡中的解离。
Sad1 counteracts Brr2-mediated dissociation of U4/U6.U5 in tri-snRNP homeostasis.
机构信息
Molecular Cell Biology, Taiwan International Graduate Program, Institute of Molecular Biology, Academia Sinica, and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan.
出版信息
Mol Cell Biol. 2014 Jan;34(2):210-20. doi: 10.1128/MCB.00837-13. Epub 2013 Nov 4.
The yeast Sad1 protein was previously identified in a screen for factors involved in the assembly of the U4/U6 di-snRNP particle. Sad1 is required for pre-mRNA splicing both in vivo and in vitro, and its human orthologue has been shown to associate with U4/U6.U5 tri-snRNP. We show here that Sad1 plays a role in maintaining a functional form of the tri-snRNP by promoting the association of U5 snRNP with U4/U6 di-snRNP. In the absence of Sad1, the U4/U6.U5 tri-snRNP dissociates into U5 and U4/U6 upon ATP hydrolysis and cannot bind to the spliceosome. The separated U4/U6 and U5 can reassociate upon incubation more favorably in the absence of ATP and in the presence of Sad1. Brr2 is responsible for mediating ATP-dependent dissociation of the tri-snRNP. Our results demonstrate a role of Sad1 in maintaining the integrity of the tri-snRNP by counteracting Brr2-mediated dissociation of tri-snRNP and provide insights into homeostasis of the tri-snRNP.
酵母 Sad1 蛋白先前在参与 U4/U6 二 snRNP 颗粒组装的因子筛选中被鉴定出来。Sad1 在体内和体外的前体 mRNA 剪接中都是必需的，其人类同源物已被证明与 U4/U6.U5 三 snRNP 相关联。我们在这里表明，Sad1 通过促进 U5 snRNP 与 U4/U6 二 snRNP 的结合，在维持三 snRNP 的功能形式方面发挥作用。在没有 Sad1 的情况下，三 snRNP 在 ATP 水解时会解离成 U5 和 U4/U6，并且不能与剪接体结合。在没有 ATP 的情况下，分离的 U4/U6 和 U5 在孵育时更有利于在 Sad1 的存在下重新结合。Brr2 负责介导三 snRNP 的 ATP 依赖性解离。我们的结果表明，Sad1 通过拮抗 Brr2 介导的三 snRNP 解离来维持三 snRNP 的完整性，并为三 snRNP 的动态平衡提供了见解。
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