Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan 115, Republic of China.
Mol Cell Biol. 2011 Jan;31(1):43-53. doi: 10.1128/MCB.00801-10. Epub 2010 Oct 18.
Cwc22 was previously identified to associate with the pre-mRNA splicing factor Cef1/Ntc85, a component of the Prp19-associated complex (nineteen complex [NTC]) involved in spliceosome activation. We show here that Cwc22 is required for pre-mRNA splicing both in vivo and in vitro but is neither tightly associated with the NTC nor required for spliceosome activation. Cwc22 is associated with the spliceosome prior to catalytic steps and remains associated throughout the reaction. The stable association of Cwc22 with the spliceosome requires the presence of the NTC but is independent of Prp2. Although Cwc22 is not required for the recruitment of Prp2 to the spliceosome, it is essential for the function of Prp2 in promoting the release of the U2 components SF3a and SF3b. In the absence of Cwc22, Prp2 can bind to the spliceosome but is dissociated upon ATP hydrolysis without promoting the release of SF3a/b. Thus, Cwc22 represents a novel ATP-dependent step one factor besides Prp2 and Spp2 and has a distinct role from that of Spp2 in mediating the function of Prp2.
Cwc22 先前被鉴定与 pre-mRNA 剪接因子 Cef1/Ntc85 相关，后者是参与剪接体激活的 Prp19 相关复合物（nineteen complex [NTC]）的一个组成部分。我们在此表明，Cwc22 在体内和体外都需要进行 pre-mRNA 剪接，但既与 NTC 没有紧密关联，也不是剪接体激活所必需的。Cwc22 在催化步骤之前与剪接体相关联，并在整个反应过程中保持关联。Cwc22 与剪接体的稳定关联需要 NTC 的存在，但不依赖于 Prp2。尽管 Cwc22 对于 Prp2 招募到剪接体不是必需的，但它对于 Prp2 促进 U2 成分 SF3a 和 SF3b 的释放的功能是必不可少的。在没有 Cwc22 的情况下，Prp2 可以结合到剪接体上，但在没有促进 SF3a/b 释放的情况下，在 ATP 水解时会被解离。因此，Cwc22 代表了除 Prp2 和 Spp2 之外的一个新的 ATP 依赖性步骤，并且在介导 Prp2 的功能方面具有与 Spp2 不同的作用。
