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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Closing the gaps in kinetoplast DNA network replication
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Closing the gaps in kinetoplast DNA network replication

机译：缩小动素体DNA网络复制的差距

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Trypanosomatids are protozoan parasites responsible for important tropical diseases. One example, Trypanosoma brucei, causes African sleeping sickness, and related parasites cause Chagas disease and leishmaniasis. Because they are among the earliest-branching eukary-otes, trypanosomatids have unusual biological properties. One of their most curious features is a unique mitochondrial DNA network known as kinetoplast DNA (kDNA). The kDNA network is composed of several thousand mini-circles that are interlocked like the links in medieval chain mail. Also intertwined in the network are a few dozen maxi-circles. See Fig. 1 for an electron micrograph of a segment of an isolated kDNA network from Crithidia fascicu-lata, a trypanosomatid often studied because it is nonpathogenic and easy to cultivate. The function of kDNA maxi-circles, like mitochondrial DNA in conventional eukaryotes, is to encode a few gene products such as rRNA and sub-units of respiratory complexes. However, the mechanism of gene expression is highly unconventional in that maxi-circle transcripts must be edited to form a functional mRNA. Editing is an amazing form of RNA processing in which uridine residues are inserted or deleted at precise internal sites within the maxi-circle transcripts, generating ORFs. Mini circles encode guide RNAs that are templates for editing of maxicircle transcripts. See ref. 2 for a review of editing and ref. 3 for a discussion of the evolution of kDNA and the significance of the network structure.
机译：锥虫是引起重要热带疾病的原生动物寄生虫。一个例子是布鲁氏锥虫，它引起非洲昏睡病，而相关的寄生虫则引起恰加斯病和利什曼病。由于锥虫属于最早分支的真核生物，因此具有异常的生物学特性。他们最奇怪的特征之一是独特的线粒体DNA网络，称为动质体DNA（kDNA）。 kDNA网络由数千个微型圆圈组成，它们像中世纪链锁中的链接一样互锁。网络中还缠绕着几十个最大圆。取自Crithidia fascicu-lata的分离的kDNA网络的一部分的电子显微图，见图1，它是一种经常被研究的锥虫，因为它不致病且易于培养。与传统的真核生物中的线粒体DNA一样，kDNA最大圆的功能是编码一些基因产物，例如rRNA和呼吸系统复合物的亚基。但是，基因表达的机制非常不常规，因为必须编辑最大圆环转录本才能形成功能性mRNA。编辑是RNA处理的一种令人惊奇的形式，其中尿苷残基被插入或缺失到大环转录物的精确内部位点，从而产生ORF。小圆圈编码指导RNA，指导RNA是用于编辑大环转录本的模板。参见参考。 2编辑和参考的复习。图3讨论了kDNA的进化和网络结构的重要性。

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