真核生物DNA连接酶Ⅲ的功能演化

摘要

DNA连接酶Ⅲ被认为只存在于脊椎动物,并在细胞核DNA的修复和线粒体DNA的复制和修复过程中发挥功能.虽然近来有关于无脊椎动物中存在着DNA连接酶Ⅲ的报道,但其功能演化及在无脊椎动物中的分布仍不清楚.为进一步探讨DNA连接酶Ⅲ的功能演化,进行了数据库搜索、线粒体定位信号(MLS)预测和功能位点保守性分析等.研究结果显示:DNA连接酶Ⅲ在变形虫、动物界和领鞭毛虫中广泛存在,但其在真菌界等发生整个蛋白或部分结构域的丢失；很多物种的DNA连接酶Ⅲ不含线粒体定位信号,因此,它们不太可能在线粒体中发挥作用,而参与细胞核DNA的修复是DNA连接酶Ⅲ较为古老和保守的功能.%Previous studies revealed that DNA ligase III was restricted to vertebrates and functioned in nucleus DNA repair and mitochondria DNA replication and repair. Although recent researches have reported that DNA ligase m is also found in non-vertebrates, little attention has been devoted to the distribution and functional evolution of DNA ligase III. To probe the functional evolution of DNA ligase III , database searches, mitochondrial localization signal prediction (MLS) and functional conservation analysis were performed. The results show that, DNA ligase III can be observed in amoebozoa, metazoa and choanoflagellates, but the whole protein or some domains are lost in some species including fungi. The MLS prediction analysis suggests that, the DNA ligase III in many species can not function in mitochondria, and is consequently less likely to play a role for DNA ligase III in mitochondria. The conservation analyses of functional site demonstrate that nucleus DNA repair is an ancient and conserved function of DNA ligase III.