Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskiye Gory 1-40, Moscow 119991, Russian Federation.
Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow 127994, Russian Federation.
Nucleic Acids Res. 2019 Jul 26;47(13):6858-6870. doi: 10.1093/nar/gkz517.
Inverted repeats are common DNA elements, but they rarely overlap with protein-coding sequences due to the ensuing conflict with the structure and function of the encoded protein. We discovered numerous perfect inverted repeats of considerable length (up to 284 bp) embedded within the protein-coding genes in mitochondrial genomes of four Nematomorpha species. Strikingly, both arms of the inverted repeats encode conserved regions of the amino acid sequence. We confirmed enzymatic activity of the respiratory complex I encoded by inverted repeat-containing genes. The nucleotide composition of inverted repeats suggests strong selection at the amino acid level in these regions. We conclude that the inverted repeat-containing genes are transcribed and translated into functional proteins. The survey of available mitochondrial genomes reveals that several other organisms possess similar albeit shorter embedded repeats. Mitochondrial genomes of Nematomorpha demonstrate an extraordinary evolutionary compromise where protein function and stringent secondary structure elements within the coding regions are preserved simultaneously.
反向重复序列是常见的 DNA 元件，但由于与编码蛋白的结构和功能产生冲突，它们很少与蛋白质编码序列重叠。我们在四种线虫动物线粒体基因组的蛋白质编码基因中发现了许多相当长（长达 284 个碱基对）的完美反向重复序列。引人注目的是，反向重复序列的两个臂都编码氨基酸序列的保守区。我们证实了由含有反向重复序列的基因编码的呼吸复合物 I 的酶活性。反向重复序列的核苷酸组成表明这些区域在氨基酸水平上受到强烈选择。我们得出结论，含有反向重复序列的基因被转录并翻译成有功能的蛋白质。对现有线粒体基因组的调查显示，其他几种生物也具有类似但较短的嵌入重复序列。线虫动物的线粒体基因组表现出一种非凡的进化妥协，其中编码区域内的蛋白质功能和严格的二级结构元件同时得到保留。
