Huang Tao, Vilardell Josep, Query Charles C
Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461-1975, USA.
EMBO J. 2002 Oct 15;21(20):5516-26. doi: 10.1093/emboj/cdf555.
We have initiated a biochemical analysis of splicing complexes in extracts from the fission yeast Schizosaccharomyces pombe. Extracts of S.pombe contain high levels of the spliceosome-like U2/5/6 tri-snRNP, which dissociates into mono-snRNPs in the presence of ATP, and supports binding of U2 snRNP to the 3' end of introns, yielding a weak ATP-independent E complex and the stable ATP-dependent complex A. The requirements for S.pombe complex A formation (pre-mRNA sequence elements, protein splicing factors, SF1/BBP and both subunits of U2AF) are analogous to those of mammalian complex A. The S.pombe SF1/BBP, U2AF(59) and U2AF(23) are tightly associated in a novel complex that is required for complex A formation. This pre-formed SF1- U2AF(59)-U2AF(23) complex may represent a streamlined mechanism for recognition of the branch site, pyrimidine tract and 3' splice site at the 3' end of introns.
我们已经开始对裂殖酵母粟酒裂殖酵母提取物中的剪接复合体进行生化分析。粟酒裂殖酵母提取物含有高水平的剪接体样U2/5/6三小核核糖核蛋白，其在ATP存在下会解离成单小核核糖核蛋白，并支持U2小核核糖核蛋白与内含子3'末端结合，产生一个弱的不依赖ATP的E复合体和稳定的依赖ATP的复合体A。粟酒裂殖酵母复合体A形成的要求（前体mRNA序列元件、蛋白质剪接因子、SF1/BBP和U2AF的两个亚基）与哺乳动物复合体A的要求相似。粟酒裂殖酵母的SF1/BBP、U2AF(59)和U2AF(23)紧密结合在一个新的复合体中，该复合体是复合体A形成所必需的。这种预先形成的SF1-U2AF(59)-U2AF(23)复合体可能代表了一种简化的机制，用于识别内含子3'末端的分支位点、嘧啶序列和3'剪接位点。
