Rantanen Anja, Gaspari Martina, Falkenberg Maria, Gustafsson Claes M, Larsson Nils-Göran
Department of Medical Nutrition, Karolinska Institutet, NOVUM, Huddinge Hospital, S-14186 Huddinge, Sweden.
Mamm Genome. 2003 Jan;14(1):1-6. doi: 10.1007/s00335-002-2218-z.
We have recently fully reconstituted the basal human mitochondrial transcription machinery in a pure in vitro system. Surprisingly, we found two different transcription factors (TFB1M and TFB2M) that each interact with mitochondrial RNA polymerase in human mitochondria, whereas there is only one such factor in budding yeast mitochondria. This unexpected finding raised important questions concerning the regulation of mitochondrial transcription in mammals in general and in other metazoans. We have now further analyzed putative homologs to TFB1M and TFB2M in different species. We mapped the mouse homologs, Tfb1m and Tfb2m, by linkage analysis to mouse Chr 17 and Chr 1, respectively. These regions display conserved linkage synteny with human Chr 6 and Chr 1, where TFB1M and TFB2M map. The intron-exon arrangements of Tfb1m and TFB1M and of Tfb2m and TFB2M were identical, and the promoter regions had similar predicted recognition elements for transcriptional factors NRF2 and Sp1. Northern blot analyses showed that Tfb1m and Tfb2m were ubiquitously expressed and had expression patterns that were very similar to the previously reported expression patterns for TFB1M and TFB2M. These findings show that Tfb1m and Tfb2m indeed are orthologs to TFB1M and TFB2M. Bioinformatic analyses indicated that most metazoans have two TFBM genes, since putative homologs to both TFB1M and TFB2M were found in D. melanogaster. Our data thus suggest that a duplication event of the TFBM gene in early metazoan evolution has permitted a more flexible regulation of mtDNA transcription, possibly in response to the complex physiological demands of multicellular organisms.
最近，我们在一个纯体外系统中完全重构了基础人类线粒体转录机制。令人惊讶的是，我们发现了两种不同的转录因子（TFB1M和TFB2M），它们各自在人类线粒体中与线粒体RNA聚合酶相互作用，而在芽殖酵母线粒体中只有一种这样的因子。这一意外发现引发了关于哺乳动物及其他后生动物中线粒体转录调控的重要问题。我们现在进一步分析了不同物种中TFB1M和TFB2M的假定同源物。通过连锁分析，我们将小鼠同源物Tfb1m和Tfb2m分别定位到小鼠的17号染色体和1号染色体上。这些区域与TFB1M和TFB2M所在的人类6号染色体和1号染色体显示出保守的连锁同线性。Tfb1m与TFB1M以及Tfb2m与TFB2M的内含子 - 外显子排列相同，并且启动子区域对转录因子NRF2和Sp1具有相似的预测识别元件。Northern印迹分析表明，Tfb1m和Tfb2m广泛表达，其表达模式与先前报道的TFB1M和TFB2M的表达模式非常相似。这些发现表明，Tfb1m和Tfb2m确实是TFB1M和TFB2M的直系同源物。生物信息学分析表明，大多数后生动物有两个TFBM基因，因为在黑腹果蝇中发现了TFB1M和TFB2M的假定同源物。因此，我们的数据表明，后生动物早期进化过程中TFBM基因的一次复制事件可能允许对线粒体DNA转录进行更灵活的调控，这可能是对多细胞生物复杂生理需求的一种响应。
