Conrad-Webb H, Perlman P S, Zhu H, Butow R A
Department of Molecular Genetics, Ohio State University, Columbus 43210-1292.
Nucleic Acids Res. 1990 Mar 25;18(6):1369-76. doi: 10.1093/nar/18.6.1369.
The SUV3-1 mutation was isolated earlier as a suppressor of a deletion of a conserved RNA processing site (dodecamer) near the 3' end of the var1 gene. Previous studies indicate that the suppressor enhances translation of mutant var1 messages; unexpectedly, it also causes over-accumulation of excised intron RNA of the large rRNA gene intron and blocks cleavage at the dodecamer site within that intron. In this study most mitochondrial genes in SUV3-1 and suv3 nuclear contexts are surveyed for changes in levels of mRNA, for interference with dodecamer cleavage and splicing and for levels of excised intron RNAs. SUV3-1 has little or no effect on the size or abundance of unspliced RNAs tested. It results, however, in a marked increase in the abundance of seven of eight excised group I intron RNAs tested, most of which are not detectable in wild-type (suv3) strains. The suppressor lowers levels of the cob and coxl mRNAs about 2-5 and 20-fold, respectively. The effect on coxl mRNA results from a decrease in the splicing of its intron 5 beta. Despite the reduction in these mRNA levels, the amounts of coxl and cyt b polypeptides were close to wild-type levels in SUV3-1 cells. These data show that the suv3 gene plays a prominent role in post-transcriptional and translation events in yeast mitochondria.
SUV3-1突变体是先前作为var1基因3'端附近保守RNA加工位点（十二聚体）缺失的抑制子而分离得到的。先前的研究表明，该抑制子增强了突变var1信息的翻译；出乎意料的是，它还导致大rRNA基因内含子的切除内含子RNA过度积累，并阻断该内含子内十二聚体位点的切割。在本研究中，对SUV3-1和suv3核背景下的大多数线粒体基因进行了检测，以观察mRNA水平的变化、对十二聚体切割和剪接的干扰以及切除内含子RNA的水平。SUV3-1对所测试的未剪接RNA的大小或丰度几乎没有影响。然而，它导致所测试的八个切除的I类内含子RNA中的七个丰度显著增加，其中大多数在野生型（suv3）菌株中无法检测到。该抑制子分别使cob和coxl mRNA水平降低约2-5倍和20倍。对coxl mRNA的影响是由于其内含子5β剪接减少所致。尽管这些mRNA水平降低，但SUV3-1细胞中coxl和细胞色素b多肽的量接近野生型水平。这些数据表明，suv3基因在酵母线粒体的转录后和翻译事件中起重要作用。
