The Saccharomyces cerevisiae genome contains 6572 ORFs, of which 680 ORFs are classified as dubious ORFs. A dubious ORF is a small, noncoding, nonconserved ORF that overlaps with another ORF of the complementary strand. Our study characterizes a dubious/nondubious ORF pair, YPR099C/MRPL51, and shows the transcript and protein level expression of YPR099C. Its subcellular localization was observed in the mitochondria. The overlapping ORF, MRPL51, encodes a mitochondrial ribosomal protein of large subunit. Deletion of any ORF from YPR099C/MRPL51 pair induces common phenotypes, i.e. loss of mtDNA, lack of mitochondrial fusion and lack of respiratory growth, due to the double deletion (ypr099cΔ/Δmrpl51Δ/Δ) caused by sequence overlap. Hence, we created the single deletions of each ORF of the YPR099C/MRPL51 pair by an alternative approach to distinguish their phenotypes and identify the specific functions. Both the ORFs were found essential for the functional mitochondria and respiratory growth, but MRPL51 showed its specific requirement in mtDNA stability. The mechanism of mtDNA maintenance by Mrpl51 is probably Mhr1 dependent that physically interacts with Mrpl51 and also regulates mtDNA repair. Overall, our study provides strong evidence for the protein level expression of a dubious ORF YPR099C and the bifunctional role of Mrpl51 in mtDNA maintenance.

中文翻译：

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酵母YPR099C / MRPL51的反向遗传分析显示，重叠的ORF在呼吸生长中和MRPL51在线粒体DNA维持中都起着关键作用。

酿酒酵母基因组包含6572个ORF，其中680个ORF被归类为可疑ORF。可疑的ORF是与互补链的另一个ORF重叠的小的非编码，非保守ORF。我们的研究表征了一个可疑/非可疑ORF对，YPR099C / MRPL51，并显示了YPR099C的转录本和蛋白质水平表达。在线粒体中观察到其亚细胞定位。重叠的ORF MRPL51编码大亚基的线粒体核糖体蛋白。由于序列重叠引起的双重缺失（ypr099cΔ/Δmrp151Δ/Δ），从YPR099C / MRPL51对中删除任何ORF会诱导常见的表型，即mtDNA缺失，线粒体融合缺乏和呼吸生长缺乏。因此，我们通过替代方法创建了YPR099C / MRPL51对的每个ORF的单个缺失，以区分它们的表型并鉴定特定功能。发现两个ORF对功能性线粒体和呼吸生长至关重要，但是MRPL51显示了其对mtDNA稳定性的特定要求。Mrpl51维持mtDNA的机制可能是Mhr1依赖性的，它与Mrpl51发生物理相互作用，并调节mtDNA的修复。总体而言，我们的研究为可疑的ORF YPR099C的蛋白水平表达以及Mrpl51在mtDNA维持中的双重功能提供了有力的证据。Mrpl51维持mtDNA的机制可能是Mhr1依赖性的，它与Mrpl51发生物理相互作用，并调节mtDNA的修复。总体而言，我们的研究为可疑的ORF YPR099C的蛋白水平表达以及Mrpl51在mtDNA维持中的双重功能提供了有力的证据。Mrpl51维持mtDNA的机制可能是Mhr1依赖性的，它与Mrpl51发生物理相互作用，并调节mtDNA的修复。总体而言，我们的研究为可疑的ORF YPR099C的蛋白水平表达以及Mrpl51在mtDNA维持中的双重功能提供了有力的证据。