A complex organization of the gene encoding cytochrome oxidase subunit 1 in the mitochondrial genome of the dinoflagellate, Crypthecodinium cohnii:: Homologous recombination generates two different cox1 open reading frames
A complex organization of the gene encoding cytochrome oxidase subunit 1 in the mitochondrial genome of the dinoflagellate, Crypthecodinium cohnii:: Homologous recombination generates two different cox1 open reading frames
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DOI：
10.1007/s002390010225
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发表时间：
2001-10-01
影响因子：
3.9
通讯作者：
Gray, MW
中科院分区：
文献类型：
--
作者：
Norman, JE;Gray, MW
在研究 Crypthecodinium cohnii（一种非光合甲藻）的线粒体基因组组织过程中，我们鉴定了四个 EcoRI 片段，它们与 cox1（编码细胞色素氧化酶亚基 1 的基因）特异的探针杂交。四个片段（5.7、5.1、4.1、3.5 KB 对）的克隆和序列表征表明，cox1 存在于 C. cohnii mtDNA 的四个不同但相关的环境中，中央重复单元两侧是两个可能的上游（侧翼结构域 1 或 2）和下游（侧翼结构域 3 或 4）区域之一。 cox1 基因的大部分位于中央重复序列内；然而，开放阅读框的 C 端部分延伸至侧翼结构域 3 和 4，从而产生两个不同的 cox1 编码序列。 cox1 阅读框之一的 3' 末端区域可以呈现出复杂的二级结构，该结构可能起到稳定成熟 mRNA 的作用，防止溶核降解。此外，在 cox1 的 5' 端发现了高密度的小反向重复序列（15-22 个碱基对），进一步表明发夹结构对于基因调控可能很重要。 Cox1 在 C. cohnii mtDNA 中的组织似乎反映了不同 cox1 序列背景之间中央重复内的同源重组事件。这种重组重复是植物（被子植物）mtDNA 的一个特征，但它们以前没有在原生生物的线粒体基因组中被描述过。
In the course of investigating mitochondrial genome organization in Crypthecodinium cohnii, a non-photosynthetic dinoflagellate, we identified four EcoRI fragments that hybridize to a probe specific for cox1, the gene that encodes subunit 1 of cytochrome oxidase. Cloning and sequence characterization of the four fragments (5.7, 5.1, 4.1, 3.5 kilobase pairs) revealed that cox1 exists in four distinct but related contexts in C. cohnii mtDNA, with a central repeat unit flanked by one of two possible upstream (flanking domain 1 or 2) and downstream (flanking domain 3 or 4) regions. The majority of the cox1 gene is located within the central repeat; however, the C-terminal portion of the open reading frame extends into flanking domains 3 and 4, thereby creating two distinct cox1 coding sequences. The 3'-terminal region of one of the cox1 reading frames can assume an elaborate secondary structure, which potentially could act to stabilize the mature mRNA against nucleolytic degradation. In addition, a high density of small inverted repeats (15-22 base pairs) has been identified at the 5'-end of cox1, further suggesting that hairpin structures could be important for gene regulation. The organization of cox1 in C. cohnii mtDNA appears to reflect homologous recombination events within the central repeat between different cox1 sequence contexts. Such recombining repeats are a characteristic feature of plant (angiosperm) mtDNA, but they have not previously been described in the mitochondrial genomes of protists.