Incorvaia R, Padgett R A
Department of Molecular Biology, The Lerner Research Institute, The Cleveland Clinic Foundation, Ohio 44195, USA.
RNA. 1998 Jun;4(6):709-18. doi: 10.1017/s1355838298980207.
The minor U12-dependent class of eukaryotic nuclear pre-mRNA introns is spliced by a distinct spliceosomal mechanism that requires the function of U11, U12, U5, U4atac, and U6atac snRNAs. Previous work has shown that U11 snRNA plays a role similar to U1 snRNA in the major class spliceosome by base pairing to the conserved 5' splice site sequence. Here we show that U6atac snRNA also base pairs to the 5' splice site in a manner analogous to that of U6 snRNA in the major class spliceosome. We show that splicing defective mutants of the 5' splice site can be activated for splicing in vivo by the coexpression of compensatory U6atac snRNA mutants. In some cases, maximal restoration of splicing required the coexpression of compensatory U11 snRNA mutants. The allelic specificity of mutant phenotype suppression is consistent with Watson-Crick base pairing between the pre-mRNA and the snRNAs. These results provide support for a model of the RNA-RNA interactions at the core of the U12-dependent spliceosome that is strikingly similar to that of the major class U2-dependent spliceosome.
真核细胞核前体mRNA中较小的依赖U12的内含子类别，通过一种独特的剪接体机制进行剪接，该机制需要U11、U12、U5、U4atac和U6atac snRNA发挥作用。先前的研究表明，U11 snRNA在主要类别剪接体中通过与保守的5'剪接位点序列碱基配对，发挥着与U1 snRNA类似的作用。在此我们表明，U6atac snRNA也以类似于主要类别剪接体中U6 snRNA的方式与5'剪接位点碱基配对。我们发现，5'剪接位点的剪接缺陷突变体可通过共表达补偿性U6atac snRNA突变体在体内被激活进行剪接。在某些情况下，剪接的最大恢复需要共表达补偿性U11 snRNA突变体。突变体表型抑制的等位基因特异性与前体mRNA和snRNA之间的沃森-克里克碱基配对一致。这些结果为依赖U12的剪接体核心处的RNA-RNA相互作用模型提供了支持，该模型与主要类别依赖U2的剪接体的模型惊人地相似。
