在许多真核生物中,Argonaute蛋白,由短RNA序列指导,保护细胞免受转座子和病毒的侵害。在嗜热真细菌中,DNA引导的ArgonauteTtAgo防御DNA质粒的转化。这里,我们报道TtAgo也参与DNA复制。在体内,TtAgo结合源自复制终止的染色体区域的15-至18-ntDNA向导,并与已知在DNA复制中起作用的蛋白质缔合。当旋转酶,唯一的嗜热T.II型拓扑异构酶,被抑制,TtAgo允许细菌完成其环状基因组的复制。相比之下,促旋酶和TtAgo活性的丧失会减慢生长并产生长的香肠状细丝,其中单个细菌通过DNA连接。最后,野生型嗜热T.Thermophus胜过缺乏TtAgo的其他等基因菌株。我们认为TtAgo的主要作用是帮助嗜热T.thermophilus解开DNA复制产生的连锁环状染色体。
In many eukaryotes, Argonaute proteins, guided by short RNA sequences, defend cells against transposons and viruses. In the eubacterium Thermus thermophilus, the DNA-guided Argonaute TtAgo defends against transformation by DNA plasmids. Here, we report that TtAgo also participates in DNA replication. In vivo, TtAgo binds 15- to 18-nt DNA guides derived from the chromosomal region where replication terminates and associates with proteins known to act in DNA replication. When gyrase, the sole T. thermophilus type II topoisomerase, is inhibited, TtAgo allows the bacterium to finish replicating its circular genome. In contrast, loss of gyrase and TtAgo activity slows growth and produces long sausage-like filaments in which the individual bacteria are linked by DNA. Finally, wild-type T. thermophilus outcompetes an otherwise isogenic strain lacking TtAgo. We propose that the primary role of TtAgo is to help T. thermophilus disentangle the catenated circular chromosomes generated by DNA replication.