Tominaga K, Hayashi J, Kagawa Y, Ohta S
Department of Biochemistry, Jichi Medical School, Japan.
Biochem Biophys Res Commun. 1993 Jul 15;194(1):544-51. doi: 10.1006/bbrc.1993.1854.
Mitochondrial transcriptional factor 1 (mtTF1) is required for both transcription and replication of mammalian mitochondrial DNA (mtDNA) and it has two consensus sequences of HMG (high mobility group) boxes. In studies on the regulation of gene expression of mtTF1, we examined the steady state level of the mRNA in cultured HeLa cells. We found that in addition to the major mRNA, 30% of the mRNA of mtTF1 in the cells was a smaller isoform with a 96 base deletion. This smaller mRNA was also found in most human tissues. The region of the deletion corresponds to the second HMG-box, which may interact directly with DNA. We examined the structure of the genomic gene encoding the human mtTF1 to determine the mechanism of the deletion. We found that the gene is composed of 7 exons spanning over 10 kilobase-pairs and that its 5th exon is identical to the 96 bases skipped in the shorter mRNA. Therefore, the shorter mtTF1 is concluded to be generated by alternative splicing.
线粒体转录因子1（mtTF1）是哺乳动物线粒体DNA（mtDNA）转录和复制所必需的，它有两个高迁移率族（HMG）盒的共有序列。在对mtTF1基因表达调控的研究中，我们检测了培养的HeLa细胞中该mRNA的稳态水平。我们发现，除了主要的mRNA外，细胞中30%的mtTF1 mRNA是一种较小的异构体，缺失了96个碱基。在大多数人类组织中也发现了这种较小的mRNA。缺失区域对应于第二个HMG盒，它可能直接与DNA相互作用。我们检测了编码人类mtTF1的基因组基因结构，以确定缺失的机制。我们发现该基因由7个外显子组成，跨越超过10千碱基对，其第5个外显子与较短mRNA中跳过的96个碱基相同。因此，得出结论，较短的mtTF1是通过可变剪接产生的。
