Dalla Rosa Ilaria, Goffart Steffi, Wurm Melanie, Wiek Constanze, Essmann Frank, Sobek Stefan, Schroeder Peter, Zhang Hongliang, Krutmann Jean, Hanenberg Helmut, Schulze-Osthoff Klaus, Mielke Christian, Pommier Yves, Boege Fritz, Christensen Morten O
Institute of Clinical Chemistry and Laboratory Diagnostics, Heinrich-Heine-University, Medical School, D-40225 Düsseldorf, Germany.
Nucleic Acids Res. 2009 Oct;37(19):6414-28. doi: 10.1093/nar/gkp708. Epub 2009 Aug 31.
Topoisomerase I is essential for DNA metabolism in nuclei and mitochondria. In yeast, a single topoisomerase I gene provides for both organelles. In vertebrates, topoisomerase I is divided into nuclear and mitochondrial paralogs (Top1 and Top1mt). To assess the meaning of this gene duplication, we targeted Top1 to mitochondria or Top1mt to nuclei. Overexpression in the fitting organelle served as control. Targeting of Top1 to mitochondria blocked transcription and depleted mitochondrial DNA. This was also seen with catalytically inactive Top1 mutants, but not with Top1mt overexpressed in mitochondria. Targeting of Top1mt to the nucleus revealed that it was much less able to interact with mitotic chromosomes than Top1 overexpressed in the nucleus. Similar experiments with Top1/Top1mt hybrids assigned these functional differences to structural divergences in the DNA-binding core domains. We propose that adaptation of this domain to different chromatin environments in nuclei and mitochondria has driven evolutional development and conservation of organelle-restricted topoisomerase I paralogs in vertebrates.
拓扑异构酶I对于细胞核和线粒体中的DNA代谢至关重要。在酵母中，单个拓扑异构酶I基因负责这两种细胞器的相关功能。在脊椎动物中，拓扑异构酶I分为核型和线粒体型旁系同源物（Top1和Top1mt）。为了评估这种基因复制的意义，我们将Top1靶向线粒体或将Top1mt靶向细胞核，并以在合适细胞器中的过表达作为对照。将Top1靶向线粒体可阻断转录并耗尽线粒体DNA。催化失活的Top1突变体也出现这种情况，但线粒体中过表达的Top1mt则不会。将Top1mt靶向细胞核发现，与细胞核中过表达的Top1相比，它与有丝分裂染色体相互作用的能力要弱得多。对Top1/Top1mt杂交体进行的类似实验将这些功能差异归因于DNA结合核心结构域的结构差异。我们认为，该结构域适应细胞核和线粒体中不同的染色质环境推动了脊椎动物中细胞器特异性拓扑异构酶I旁系同源物的进化发展和保守性。
