Matsushima Yuichi, Adán Cristina, Garesse Rafael, Kaguni Laurie S
Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824-1319, USA.
J Biol Chem. 2005 Apr 29;280(17):16815-20. doi: 10.1074/jbc.M500569200. Epub 2005 Mar 3.
We report the cloning and molecular analysis of Drosophila mitochondrial transcription factor (d-mtTF) B1. An RNA interference (RNAi) construct was designed that reduces expression of d-mtTFB1 to 5% of its normal level in Schneider cells. In striking contrast with our previous study on d-mtTFB2, we found that RNAi knock-down of d-mtTFB1 does not change the abundance of specific mitochondrial RNA transcripts, nor does it affect the copy number of mitochondrial DNA. In a corollary manner, overexpression of d-mtTFB1 did not increase either the abundance of mitochondrial RNA transcripts or mitochondrial DNA copy number. Our data suggest that, unlike d-mtTFB2, d-mtTFB1 does not have a critical role in either transcription or regulation of the copy number of mitochondrial DNA. Instead, because we found that RNAi knockdown of d-mtTFB1 reduces mitochondrial protein synthesis, we propose that it serves its primary role in modulating translation. Our work represents the first study to document the role of mtTFB1 in vivo and establishes clearly functional differences between mtTFB1 and mtTFB2.
我们报告了果蝇线粒体转录因子（d-mtTF）B1的克隆及分子分析。设计了一种RNA干扰（RNAi）构建体，其可将施奈德细胞中d-mtTFB1的表达降低至正常水平的5%。与我们之前对d-mtTFB2的研究形成鲜明对比的是，我们发现RNAi敲低d-mtTFB1并不会改变特定线粒体RNA转录本的丰度，也不会影响线粒体DNA的拷贝数。相应地，d-mtTFB1的过表达也不会增加线粒体RNA转录本的丰度或线粒体DNA拷贝数。我们的数据表明，与d-mtTFB2不同，d-mtTFB1在转录或线粒体DNA拷贝数的调控中均不发挥关键作用。相反，由于我们发现RNAi敲低d-mtTFB1会降低线粒体蛋白质合成，我们提出它在调节翻译中发挥主要作用。我们的工作是第一项记录mtTFB1在体内作用的研究，并明确确立了mtTFB1和mtTFB2之间的功能差异。
