Colot H V, Stutz F, Rosbash M
Howard Hughes Medical Institute, Brandeis University, Department of Biology, Waltham, Massachusetts 02254, USA.
Genes Dev. 1996 Jul 1;10(13):1699-708. doi: 10.1101/gad.10.13.1699.
The mechanism by which pre-mRNAs are initially recognized by the splicing machinery is not well understood. In the yeast system, commitment complexes are the earliest identified splicing complexes. They contain pre-mRNA, U1 snRNP, and the splicing factor Mud2p and probably correspond to the mammalian E complexes, which contain pre-mRNA, U1 snRNP, and the splicing factor U2AF. To identify other yeast commitment complex components, we have characterized mutant strains that are synthetic lethal with viable U1 snRNA mutations. We report here that MUD13 is a nonessential gene that encodes the yeast homolog of CBP20, the small subunit of the vertebrate nuclear cap-binding complex (CBC). Characterization of splicing in the delta-MUD13 strain and extract indicates that Mud13p is a yeast splicing factor and is the second identified non-snRNP commitment complex component. The observations also suggest that CBC interacts with other commitment complex components as well as with the substrate cap. Taken together with the accompanying results for a mammalian system, our data indicate that cap-binding proteins as well as the pre-mRNA cap contribute to early steps in spliceosome assembly.
前体mRNA最初被剪接机制识别的机制尚未完全了解。在酵母系统中，起始复合物是最早被鉴定出的剪接复合物。它们包含前体mRNA、U1 snRNP和剪接因子Mud2p，可能对应于哺乳动物的E复合物，后者包含前体mRNA、U1 snRNP和剪接因子U2AF。为了鉴定酵母起始复合物的其他成分，我们对与存活的U1 snRNA突变体发生合成致死的突变菌株进行了表征。我们在此报告，MUD13是一个非必需基因，它编码脊椎动物核帽结合复合物（CBC）的小亚基CBP20的酵母同源物。对delta-MUD13菌株和提取物中的剪接进行表征表明，Mud13p是一种酵母剪接因子，是第二个被鉴定出的非snRNP起始复合物成分。这些观察结果还表明，CBC与其他起始复合物成分以及底物帽相互作用。结合随附的哺乳动物系统的结果，我们的数据表明帽结合蛋白以及前体mRNA帽有助于剪接体组装的早期步骤。
