Relative abundance of the human mitochondrial transcription system and distinct roles for h-mtTFB1 and h-mtTFB2 in mitochondrial biogenesis and gene expression.
Relative abundance of the human mitochondrial transcription system and distinct roles for h-mtTFB1 and h-mtTFB2 in mitochondrial biogenesis and gene expression.
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DOI：
10.1093/nar/gkm424
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发表时间：
2007
影响因子：
14.9
通讯作者：
Shadel GS
中科院分区：
文献类型：
--
作者：
Cotney J;Wang Z;Shadel GS
人类线粒体转录需要噬菌体相关的RNA聚合酶POLRMT、mtDNA结合蛋白h-mtTFA/TFAM和两种转录因子/rRNA甲基转移酶h-mtTFB 1和h-mtTFB 2。在这里，我们确定了这些核心转录成分的稳态水平，并研究了HeLa细胞中h-mtTFB 1或h-mtTFB 2有目的升高的后果。在每个分子的基础上，我们发现POLRMT比mtDNA多2.6倍，h-mtTFB 2比h-mtTFB 1多2.3倍。我们还估计h-mtTFA为1050个分子/mtDNA，预测该比例支持稳健的转录，但不覆盖mtDNA。与h-mtTFB 2在转录和转录引发的复制中的作用一致，增加的线粒体DNA和转录物是由其过表达引起的。这伴随着大多数但不是所有mtDNA编码蛋白的翻译速率增加。过表达的h-mtTFB 1没有显着影响这些参数，但确实导致线粒体生物合成增加。此外，h-mtTFB 1的mRNA和蛋白质的升高响应于h-mtTFB 2的过表达，这表明存在一个逆行信号的核协调调节这些相关因子的表达。总而言之，我们的研究结果提供了一个框架，了解人类线粒体在体内转录的调控，并定义了不同的作用，为h-mtTFB 1和h-mtTFB 2在线粒体生物合成和基因表达，一起可能微调线粒体功能。
Human mitochondrial transcription requires the bacteriophage-related RNA polymerase, POLRMT, the mtDNA-binding protein, h-mtTFA/TFAM, and two transcription factors/rRNA methyltransferases, h-mtTFB1 and h-mtTFB2. Here, we determined the steady-state levels of these core transcription components and examined the consequences of purposeful elevation of h-mtTFB1 or h-mtTFB2 in HeLa cells. On a per molecule basis, we find an ∼6-fold excess of POLRMT to mtDNA and ∼3-fold more h-mtTFB2 than h-mtTFB1. We also estimate h-mtTFA at ∼50 molecules/mtDNA, a ratio predicted to support robust transcription, but not to coat mtDNA. Consistent with a role for h-mtTFB2 in transcription and transcription-primed replication, increased mitochondrial DNA and transcripts result from its over-expression. This is accompanied by increased translation rates of most, but not all mtDNA-encoded proteins. Over-expression of h-mtTFB1 did not significantly influence these parameters, but did result in increased mitochondrial biogenesis. Furthermore, h-mtTFB1 mRNA and protein are elevated in response to h-mtTFB2 over-expression, suggesting the existence of a retrograde signal to the nucleus to coordinately regulate expression of these related factors. Altogether, our results provide a framework for understanding the regulation of human mitochondrial transcription in vivo and define distinct roles for h-mtTFB1 and h-mtTFB2 in mitochondrial biogenesis and gene expression that together likely fine-tune mitochondrial function.