Forterre P
Institut de Génétique et Microbiologie, Bat 409, CNRS, UMR 8621, Université Paris-Sud, 91405 Orsay Cedex, France.
Mol Microbiol. 1999 Aug;33(3):457-65. doi: 10.1046/j.1365-2958.1999.01497.x.
Comparative genomics has revealed many examples in which the same function is performed by unrelated or distantly related proteins in different cellular lineages. In some cases, this has been explained by the replacement of the original gene by a paralogue or non-homologue, a phenomenon known as non-orthologous gene displacement. Such gene displacement probably occurred early on in the history of proteins involved in DNA replication, repair, recombination and transcription (DNA informational proteins), i.e. just after the divergence of archaea, bacteria and eukarya from the last universal cellular ancestor (LUCA). This would explain why many DNA informational proteins are not orthologues between the three domains of life. However, in many cases, the origin of the displacing genes is obscure, as they do not even have detectable homologues in another domain. I suggest here that the original cellular DNA informational proteins have often been replaced by proteins of viral or plasmid origin. As viral and plasmid-encoded proteins are usually very divergent from their cellular counterparts, this would explain the puzzling phylogenies and distribution of many DNA informational proteins between the three domains of life.
比较基因组学揭示了许多例子，即在不同细胞谱系中，不相关或远缘相关的蛋白质执行相同的功能。在某些情况下，这可以通过旁系同源物或非同源物取代原始基因来解释，这种现象称为非直系同源基因取代。这种基因取代可能早在参与DNA复制、修复、重组和转录的蛋白质（DNA信息蛋白）的历史早期就发生了，即在古菌、细菌和真核生物从最后的普遍细胞祖先（LUCA）分化之后不久。这可以解释为什么许多DNA信息蛋白在生命的三个域之间不是直系同源物。然而，在许多情况下，取代基因的起源是模糊的，因为它们在另一个域中甚至没有可检测到的同源物。我在此提出，原始的细胞DNA信息蛋白常常被病毒或质粒起源的蛋白质所取代。由于病毒和质粒编码的蛋白质通常与其细胞对应物差异很大，这可以解释许多DNA信息蛋白在生命的三个域之间令人困惑的系统发育和分布情况。
