A novel set of spliceosome‐associated proteins and the essential splicing factor PSF bind stably to pre‐mRNA prior to catalytic step II of the splicing reaction.
A novel set of spliceosome‐associated proteins and the essential splicing factor PSF bind stably to pre‐mRNA prior to catalytic step II of the splicing reaction.
复制标题
一组新型剪接体相关蛋白和必需剪接因子 PSF 在剪接反应的催化步骤 II 之前稳定地与前 mRNA 结合。
作者：
O. Gozani;J. G. Patton;R. Reed
We have isolated and determined the protein composition of the spliceosomal complex C. The pre‐mRNA in this complex has undergone catalytic step I, but not step II, of the splicing reaction. We show that a novel set of 14 spliceosome‐associated proteins (SAPs) and the essential splicing factor PSF are specifically associated with the C complex, implicating these proteins in catalytic step II. Significantly, immunodepletion and biochemical complementation studies demonstrate directly that PSF is essential for catalytic step II. Purified PSF is known to UV crosslink to pyrimidine tracts, and our data show that PSF UV crosslinks to pre‐mRNA in purified C complex. Thus, PSF may replace the 3′ splice site binding factor U2AF65 which is destabilized during spliceosome assembly. Finally, we show that SAPs 60 and 90, which are present in both the B and C complexes, are specifically associated with U4 and U6 snRNPs, and thus may have important roles in the functioning of these snRNPs during the splicing reaction.
