Zinn A R, Butow R A
Cell. 1985 Apr;40(4):887-95. doi: 10.1016/0092-8674(85)90348-4.
A 1.1 kb intron containing an open reading frame (ORF) in one allele (omega+) of the yeast mitochondrial 21S rRNA gene is nearly quantitatively inserted in crosses into a 21S rRNA allele lacking that intron (omega-). We have determined that this nonreciprocal exchange initiates soon after cells fuse to form zygotes and is complete by 10-16 hr after mating. We have discovered a unique in vivo double-strand cut in omega- mitochondrial DNA (mtDNA) at or near the site of intron insertion that is implicated in the process. Markers flanking the intron insertion site are coconverted with frequencies inversely proportional to their distance from that site. There is no net conversion of omega- to omega+ in crosses between petites retaining these alleles, nor do we observe the unique double-strand cut in the mtDNA from zygotes of such crosses. The data suggest that a translation product of the intron ORF is required for the double-strand cut and nonreciprocal recombination at omega.
酵母线粒体21S rRNA基因的一个等位基因（ω⁺）中含有一个开放阅读框（ORF）的1.1 kb内含子，在杂交时几乎能定量地插入到缺乏该内含子的21S rRNA等位基因（ω⁻）中。我们已经确定，这种非相互交换在细胞融合形成合子后不久就开始了，并且在交配后10 - 16小时完成。我们在ω⁻线粒体DNA（mtDNA）中内含子插入位点处或其附近发现了一个独特的体内双链切割，这与该过程有关。内含子插入位点两侧的标记以与其距该位点的距离成反比的频率共同转换。在保留这些等位基因的小菌落之间的杂交中，没有ω⁻到ω⁺的净转换，我们也没有在这种杂交合子的mtDNA中观察到独特的双链切割。数据表明，内含子ORF的翻译产物是ω处双链切割和非相互重组所必需的。
