Release of SF3 from the intron branchpoint activates the first step of pre-mRNA splicing
Release of SF3 from the intron branchpoint activates the first step of pre-mRNA splicing
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DOI：
10.1261/rna.2030510
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发表时间：
2010-03-01
期刊：
影响因子：
4.5
通讯作者：
Stevens, Scott W.
中科院分区：
文献类型：
--
作者：
Lardelli, Rea M.;Thompson, James X.;Stevens, Scott W.
真核前体mRNA剪接是一个复杂的过程，需要精确的时间和>100个反式作用因子的作用。一段时间以来，人们已经知道剪接化学的两个步骤需要三个DEAH盒RNA解旋酶样蛋白;然而，它们在这些步骤中的作用机制仍然难以捉摸。剪接体逮捕在体内的三个解旋酶检查点进行纯化，第一步逮捕剪接体的功能特征。我们表明，剪接的第一步需要一个新的ATP独立的构象变化。然后Prp 2 p催化ATP依赖性重排，将SF 3a和SF 3b复合物从剪接体内的分支点置换。我们提出了一个模型，其中SF 3防止过早亲核攻击的化学反应性羟基的分支点腺苷之前的第一次酯交换。当剪接体达到正确的构象和Prp 2 p的功能时，SF 3从分支点被置换，允许第一步化学反应发生。
Eukaryotic pre-mRNA splicing is a complex process requiring the precise timing and action of >100 trans-acting factors. It has been known for some time that the two steps of splicing chemistry require three DEAH-box RNA helicase-like proteins; however, their mechanism of action at these steps has remained elusive. Spliceosomes arrested in vivo at the three helicase checkpoints were purified, and first step-arrested spliceosomes were functionally characterized. We show that the first step of splicing requires a novel ATP-independent conformational change. Prp2p then catalyzes an ATP-dependent rearrangement displacing the SF3a and SF3b complexes from the branchpoint within the spliceosome. We propose a model in which SF3 prevents premature nucleophilic attack of the chemically reactive hydroxyl of the branchpoint adenosine prior to the first transesterification. When the spliceosome attains the proper conformation and upon the function of Prp2p, SF3 is displaced from the branchpoint allowing first step chemistry to occur.