Hiasa H, Marians K J
Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
J Biol Chem. 1994 Dec 23;269(51):32655-9.
Topoisomerase III, but not topoisomerase I, could, in the absence of DNA gyrase, support bidirectional DNA replication in an oriC plasmid DNA replication system reconstituted with purified proteins. The initial rate of DNA synthesis and the efficiency of nascent chain elongation showed that topoisomerase III-stimulated DNA replication was as efficient as gyrase-stimulated DNA replication. In addition, topoisomerase III was also able, in the absence of DNA gyrase, to decatenate the replicating daughter DNA molecules to form monomer product. Thus, of the four topoisomerases in Escherichia coli, three, topoisomerases III and IV and DNA gyrase, can support nascent chain elongation, whereas only two, topoisomerases III and IV, can topologically resolve the daughter molecules.
在一个用纯化蛋白重构的oriC质粒DNA复制系统中，拓扑异构酶III而非拓扑异构酶I，在没有DNA促旋酶的情况下，能够支持双向DNA复制。DNA合成的初始速率和新生链延伸的效率表明，拓扑异构酶III刺激的DNA复制与促旋酶刺激的DNA复制效率相同。此外，拓扑异构酶III在没有DNA促旋酶的情况下，也能够解开正在复制的子代DNA分子，形成单体产物。因此，在大肠杆菌的四种拓扑异构酶中，三种，即拓扑异构酶III、IV和DNA促旋酶，能够支持新生链延伸，而只有两种，即拓扑异构酶III和IV，能够在拓扑学上解析子代分子。
