Extensive frameshift at all AGG and CCC codons in the mitochondrial cytochrome c oxidase subunit 1 gene of Perkinsus marinus (Alveolata; Dinoflagellata)
Extensive frameshift at all AGG and CCC codons in the mitochondrial cytochrome c oxidase subunit 1 gene of Perkinsus marinus (Alveolata; Dinoflagellata)
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DOI：
10.1093/nar/gkq449
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发表时间：
2010-10-01
影响因子：
14.9
通讯作者：
Kita, Kiyoshi
中科院分区：
文献类型：
--
作者：
Masuda, Isao;Matsuzaki, Motomichi;Kita, Kiyoshi
不同的线粒体（mt）遗传系统独立于更统一的核系统而进化，并且经常采用修改后的遗传密码。甲藻 mt 基因组的组织和遗传系统特别不寻常，仍然是一个进化之谜。我们确定了最早分化的甲藻 Perkinsus 的全长细胞色素 c 氧化酶亚基 1 (cox1) mRNA 序列，并表明该基因存在于 mt 基因组中。显然，该 mRNA 不能在标准密码子使用的单一阅读框中进行翻译。我们对 mRNA 的核苷酸序列和三框翻译的检查表明，每个 AGG 和 CCC 密码子的阅读框必须移动 10 次，才能产生共有的 COX1 蛋白。我们提出了这些翻译移码的两种可能机制：核糖体移码，其中停滞的核糖体跳过这些密码子的第一个碱基或识别非三联体密码子 AGGY 和 CCCCU 的专门 tRNA。无论机制如何，都需要活跃且高效的机制来耐受帕金瑟斯线粒体中预测的移码。据我们所知，这是原生生物线粒体中翻译移码的第一个证据，也是迄今为止线粒体中最广泛的案例。
Diverse mitochondrial (mt) genetic systems have evolved independently of the more uniform nuclear system and often employ modified genetic codes. The organization and genetic system of dinoflagellate mt genomes are particularly unusual and remain an evolutionary enigma. We determined the sequence of full-length cytochrome c oxidase subunit 1 (cox1) mRNA of the earliest diverging dinoflagellate Perkinsus and show that this gene resides in the mt genome. Apparently, this mRNA is not translated in a single reading frame with standard codon usage. Our examination of the nucleotide sequence and three-frame translation of the mRNA suggest that the reading frame must be shifted 10 times, at every AGG and CCC codon, to yield a consensus COX1 protein. We suggest two possible mechanisms for these translational frameshifts: a ribosomal frameshift in which stalled ribosomes skip the first bases of these codons or specialized tRNAs recognizing non-triplet codons, AGGY and CCCCU. Regardless of the mechanism, active and efficient machinery would be required to tolerate the frameshifts predicted in Perkinsus mitochondria. To our knowledge, this is the first evidence of translational frameshifts in protist mitochondria and, by far, is the most extensive case in mitochondria.