Murray J A
European Molecular Biology Laboratory, Heidelberg, FRG.
Mol Microbiol. 1987 Jul;1(1):1-4. doi: 10.1111/j.1365-2958.1987.tb00519.x.
The replication of eukaryotic DNA is normally initiated at each origin only once per cell cycle. Yet, in spite of this restriction, the 2-mu plasmid of yeast has evolved an elegant mechanism which can allow it to rapidly amplify its copy number without initiating multiple rounds of replication. It achieves this by exploiting a plasmid-encoded site-specific recombination system in a way that is apparently unique to this plasmid. The 2-mu plasmid has also evolved a mechanism that allows effective partition of itself between mother and daughter cells. Together these processes ensure the persistence of the 2-mu plasmid within a population, even though retention of the plasmid is of no advantage to the host cell and causes a slightly slower growth rate. The success of this survival strategy is illustrated by the near ubiquity of the 2-mu plasmid in both wild-type and laboratory strains of yeast.
真核生物DNA的复制通常在每个细胞周期中仅在每个起始点起始一次。然而，尽管有这种限制，酵母的2-μm质粒却进化出了一种精妙的机制，使其能够在不启动多轮复制的情况下迅速增加其拷贝数。它通过利用一种质粒编码的位点特异性重组系统来实现这一点，这种方式显然是该质粒所特有的。2-μm质粒还进化出了一种机制，使其能够在母细胞和子细胞之间有效地进行分配。这些过程共同确保了2-μm质粒在群体中的持久性，尽管保留该质粒对宿主细胞没有益处，并且会导致生长速度略有减慢。2-μm质粒在酵母的野生型菌株和实验室菌株中几乎无处不在，说明了这种生存策略的成功。
