van der Veen R, de Haan M, Grivell L A
Section for Molecular Biology, University of Amsterdam, Amsterdam, The Netherlands.
Curr Genet. 1988 Mar;13(3):219-26. doi: 10.1007/BF00387767.
We have characterized two yeast mutants deficient in the splicing of transcripts of the mitochondrial gene for cytochrome c oxidase subunit I (coxI). Both map to the first intron (aI1). RNA blot analysis shows that in addition to a reduced (mutant M15-190) or blocked (mutant M12-193) excision of the mutated intron aI1, the mutants are unable to excise the adjacent aI2 intron, the reading frame of which displays an amino acid sequence similarity to aI1. Splicing of the downstream introns is not affected, however. Sequence analysis of the first mutant DNA (M12-193) reveals a premature termination of the intron-encoded open reading frame, followed by two alterations at a short distance downstream. The other (M15-190) contains 11 separate changes. Although these occur in the intron reading frame, their main effect on RNA splicing may be exerted through the disturbance of intron secondary structure proposed for the 5' end of several group II introns. The implications of these findings in relation to maturase function and structure of intron aI1 are discussed.
我们已经鉴定出两个酵母突变体，它们在细胞色素c氧化酶亚基I（coxI）线粒体基因转录本的剪接方面存在缺陷。这两个突变体都定位于第一个内含子（aI1）。RNA印迹分析表明，除了突变的内含子aI1的切除减少（突变体M15 - 190）或受阻（突变体M12 - 193）外，这些突变体还无法切除相邻的aI2内含子，其阅读框显示出与aI1的氨基酸序列相似性。然而，下游内含子的剪接不受影响。对第一个突变体DNA（M12 - 193）的序列分析揭示了内含子编码的开放阅读框的提前终止，随后在下游短距离处有两个改变。另一个（M15 - 190）包含11个单独的变化。尽管这些变化发生在内含子阅读框中，但它们对RNA剪接的主要影响可能是通过干扰为几个II类内含子5'端提出的内含子二级结构来实现的。讨论了这些发现与成熟酶功能和内含子aI1结构的关系。
