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首页> 外文期刊>Molecular and Cellular Biology >Synthesis and turnover of mitochondrial ribonucleic acid in HeLa cells: the mature ribosomal and messenger ribonucleic acid species are metabolically unstable.
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Synthesis and turnover of mitochondrial ribonucleic acid in HeLa cells: the mature ribosomal and messenger ribonucleic acid species are metabolically unstable.

机译：HeLa细胞中线粒体核糖核酸的合成和周转：成熟的核糖体和信使核糖核酸物种在代谢上不稳定。

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The synthesis rates and half-lives of the individual mitochondrial ribosomal ribonucleic acid (RNA) and polyadenylic acid-containing RNA species in HeLa cells have been determined by analyzing their kinetics of labeling with [5-3H]-uridine and the changes in specific activity of the mitochondrial nucleotide precursor pools. In one experiment, a novel method for determining the nucleotide precursor pool specific activities, using nascent RNA chains, has been utilized. All mitochondrial RNA species analyzed were found to be metabolically unstable, with half-lives of 2.5 to 3.5 h for the two ribosomal RNA components and between 25 and 90 min for the various putative messenger RNAs. A cordycepin "chase" experiment yielded half-life values for the messenger RNA species which were, in general, larger by a factor of 1.5 to 2.5 than those estimated in the labeling kinetics experiments. On the basis of previous observations, a model is proposed whereby the rate of mitochondrial RNA decay is under feedback control by some mechanism linked to RNA synthesis or processing. A short half-life was determined for five large polyadenylated RNAs, which are probably precursors of mature species. A rate of synthesis of one to two molecules per minute per cell was estimated for the various H-strand-coded messenger RNA species, and a rate of synthesis 50 to 100 times higher was estimated for the ribosomal RNA species. These data indicate that the major portion of the H-strand in each mitochondrial deoxyribonucleic acid molecule is transcribed very infrequently, possibly as rarely as once or twice per cell generation. Furthermore, these results are consistent with a previously proposed model of H-strand transcription in the form of a single polycistronic molecule.
机译：通过分析其用[5-3H]-尿苷标记的动力学以及比活性的变化，确定了单个线粒体核糖体核糖核酸（RNA）和含聚腺苷酸的RNA种类在HeLa细胞中的合成速率和半衰期的线粒体核苷酸前体池。在一个实验中，已经使用了一种利用新生的RNA链确定核苷酸前体库比活性的新方法。发现所有分析的线粒体RNA物种在代谢上都是不稳定的，两个核糖体RNA组分的半衰期为2.5至3.5小时，而各种假定的信使RNA的半衰期为25至90分钟。虫草素“追逐”实验产生的信使RNA种类的半衰期值通常比标记动力学实验中估计的值高1.5到2.5倍。根据先前的观察结果，提出了一种模型，其中线粒体RNA衰减的速率受与RNA合成或加工相关的某种机制的反馈控制。确定了五个大的聚腺苷酸RNA的短半衰期，这些RNA可能是成熟物种的前体。对于各种H链编码的信使RNA种类，估计每细胞每分钟1至2个分子的合成速率，对于核糖体RNA种类，估计其合成速率高50至100倍。这些数据表明每个线粒体脱氧核糖核酸分子中H链的主要部分很少被转录，每细胞一代可能很少被转录一次或两次。此外，这些结果与先前提出的单个多顺反子分子形式的H链转录模型一致。

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