Couto J R, Tamm J, Parker R, Guthrie C
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448.
Genes Dev. 1987 Jul;1(5):445-55. doi: 10.1101/gad.1.5.445.
Splicing of introns from Saccharomyces cerevisiae pre-mRNA requires the conserved sequence TACTAAC; the 3'-most A residue is utilized as the site of branch formation. We showed previously that the transcript from an actin-HIS4 gene fusion containing the mutation TACTAAC to TACTACC (designated C259) is spliced inefficiently, thereby preventing growth on the histidine precursor histidinol. By selecting for growth on histidinol, we have identified a mutant in which the splicing of the C259 transcript is increased fourfold; splicing of other mutated introns is not significantly improved. The mutant locus encodes a trans-acting suppressor. A single mutation, rna16-1, is sufficient for suppression; however, suppression is maximized in heterozygous diploids containing both rna16-1 and the wild-type allele RNA16. In addition, wild-type pre-mRNAs (and lariat intermediates) accumulate in rna16-1 cells. We propose that the RNA16 locus encodes a component of the splicing machinery.
从酿酒酵母前体mRNA中剪接内含子需要保守序列TACTAAC；最靠近3'端的A残基被用作分支形成的位点。我们先前表明，一个肌动蛋白-HIS4基因融合体的转录本，其中TACTAAC突变为TACTACC（命名为C259），剪接效率低下，从而阻止了在组氨酸前体组氨醇上的生长。通过选择能在组氨醇上生长的菌株，我们鉴定出一个突变体，其中C259转录本的剪接增加了四倍；其他突变内含子的剪接没有明显改善。该突变位点编码一种反式作用抑制因子。单个突变rna16-1就足以产生抑制作用；然而，在同时含有rna16-1和野生型等位基因RNA16的杂合二倍体中抑制作用最大。此外，野生型前体mRNA（和套索中间体）在rna16-1细胞中积累。我们提出RNA16位点编码剪接机制的一个组分。
