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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Dual localization of human DNA topoisomerase IIIα to mitochondria and nucleus
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Dual localization of human DNA topoisomerase IIIα to mitochondria and nucleus

机译：人类DNA拓扑异构酶IIIα双重定位于线粒体和细胞核

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摘要

The human TOP3α gene encoding DNA topoisomerase IIIα (hTop3α) has two potential start codons for the synthesis of proteins 1, 001 and 976 aa residues in length. The sequence of the N-terminal region of the 1, 001-residue form resembles signal peptide sequences for mitochondrial import, and fluorescence microscopy shows that the addition of as few as the first 34 aa of the 1,001-residue form of hTop3α to a green fluorescent protein can direct the chimeric protein to mitochondria. Biochemical analyses of subcellular fractions of HeLa cells further demonstrate that a distinctive fraction of hTop3α is present inside mitochondria, as evidenced by its resistance to proteinase K. This fraction constitutes several percent of the enzyme in the nuclear fraction, suggesting that the distribution of the mitochondrial and nuclear forms of hTop3α is roughly in proportion to the DNA contents of these cellular compartments. The presence of a type IA DNA topoisomerase in the mitochondria of other eukaryotes is supported by an examination of the amino acid sequences of mouse and Drosophila DNA topoisomerase IIIα and Schizosaccharomyces pombe DNA topoisomerase III. Given the presence of at least one type IA DNA topoisomerase in all forms of life examined to date, the finding of a type IA enzyme in mitochondria further supports the notion of a key role of such enzymes in DNA transactions.
机译：编码DNA拓扑异构酶IIIα（hTop3α）的人TOP3α基因具有两个潜在的起始密码子，可合成长度为1、001和976个氨基酸的蛋白质。 1，001残基形式的N末端区域的序列类似于线粒体导入的信号肽序列，荧光显微镜显示，将hTop3α的1,001残基形式的前34个氨基酸添加至绿色荧光蛋白可以将嵌合蛋白引导至线粒体。对HeLa细胞亚细胞部分的生化分析进一步表明，hTop3α的独特部分存在于线粒体内，这由其对蛋白酶K的抗性证明。该部分占核部分中酶的百分之几，表明线粒体的分布hTop3α的核形式与这些细胞区室的DNA含量大致成比例。通过检查小鼠和果蝇DNA拓扑异构酶IIIα和粟酒裂殖酵母DNA拓扑异构酶III的氨基酸序列，可以证明IA型DNA拓扑异构酶存在于其他真核生物的线粒体中。考虑到迄今为止检查的所有生命形式中至少存在一种IA型DNA拓扑异构酶，线粒体中IA型酶的发现进一步支持了这种酶在DNA交易中的关键作用。

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