Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden.
EMBO Rep. 2019 Jun;20(6). doi: 10.15252/embr.201948101. Epub 2019 Apr 29.
Regulation of replication and expression of mitochondrial DNA (mtDNA) is essential for cellular energy conversion via oxidative phosphorylation. The mitochondrial transcription elongation factor (TEFM) has been proposed to regulate the switch between transcription termination for replication primer formation and processive, near genome-length transcription for mtDNA gene expression. Here, we report that is essential for mouse embryogenesis and that levels of promoter-distal mitochondrial transcripts are drastically reduced in conditional -knockout hearts. In contrast, the promoter-proximal transcripts are much increased in knockout mice, but they mostly terminate before the region where the switch from transcription to replication occurs, and consequently, mtDNA replication is profoundly reduced. Unexpectedly, deep sequencing of RNA from knockouts revealed accumulation of unprocessed transcripts in addition to defective transcription elongation. Furthermore, a proximity-labeling (BioID) assay showed that TEFM interacts with multiple RNA processing factors. Our data demonstrate that TEFM acts as a general transcription elongation factor, necessary for both gene transcription and replication primer formation, and loss of TEFM affects RNA processing in mammalian mitochondria.
线粒体 DNA（mtDNA）的复制和表达调控对于通过氧化磷酸化进行细胞能量转换至关重要。线粒体转录延伸因子（TEFM）被认为可以调节转录终止以形成复制引物与 mtDNA 基因表达的连续、接近全长转录之间的转换。在这里，我们报告说在小鼠胚胎发生过程中是必不可少的，并且条件性敲除心脏中的线粒体远端启动子转录本水平大大降低。相比之下，在 敲除小鼠中，近端启动子转录本增加了很多，但它们大多在转录到复制发生的区域之前终止，因此， mtDNA 复制受到严重抑制。出乎意料的是，对 敲除小鼠的 RNA 进行深度测序显示，除了转录延伸缺陷之外，还积累了未加工的转录本。此外，一种接近标记（BioID）测定表明，TEFM 与多种 RNA 加工因子相互作用。我们的数据表明，TEFM 作为一种通用转录延伸因子，对于基因转录和复制引物形成都是必需的，并且 TEFM 的缺失会影响哺乳动物线粒体中的 RNA 加工。
