Kennell J C, Moran J V, Perlman P S, Butow R A, Lambowitz A M
Department of Molecular Genetics, Ohio State University, Columbus 43210-1292.
Cell. 1993 Apr 9;73(1):133-46. doi: 10.1016/0092-8674(93)90166-n.
Group II introns al1 and al2 of the yeast mtDNA cox1 gene encode reverse transcriptase-like proteins that function in RNA splicing and may play a role in intron mobility and excision. We find that ribonucleoprotein particles from yeast mitochondria contain a reverse transcriptase activity that is likely encoded by al1 and al2 and is highly specific for the introns and their flanking exons. Using a mutant strain with elevated activity, we show that the reverse transcriptase uses either excised intron RNA or cox1 pre-mRNA as template and initiates cDNA synthesis near the 3' end of al2 and immediately downstream in E3. Our results suggest that introns al1 and al2 are retroelements, which encode reverse transcriptases that have adapted to function in RNA splicing.
酵母线粒体DNA的细胞色素c氧化酶亚基1（cox1）基因的Ⅱ类内含子al1和al2编码类似逆转录酶的蛋白质，这些蛋白质在RNA剪接中发挥作用，并且可能在内含子移动和切除过程中发挥作用。我们发现，来自酵母线粒体的核糖核蛋白颗粒含有一种逆转录酶活性，这种活性可能由al1和al2编码，并且对内含子及其侧翼外显子具有高度特异性。利用一个活性升高的突变菌株，我们表明该逆转录酶使用切除的内含子RNA或cox1前体mRNA作为模板，并在al2的3'端附近以及E3中紧邻下游起始cDNA合成。我们的结果表明，内含子al1和al2是逆转元件，它们编码已适应在RNA剪接中发挥作用的逆转录酶。
