Two distinct modes of strand unlinking during theta-type DNA replication.
DNA gyrase and topoisomerase IV (Topo IV) are type II bacterial DNA topoisomerases that show a high degree of similarity to each other yet appear to have different functions during DNA replication. We show here that the torsional stress generated during theta-type DNA replication in vitro can take the form of either positive supercoils ahead of the replication fork or catenane-like right-handed windings (precatenanes) of the two partially replicated duplexes behind the fork. Gyrase prefers to act on the former, whereas Topo IV prefers the latter. Removal of either form of positive winding can support nascent chain elongation, but only precatenane removal can support the final stages of DNA replication: processing of the late intermediate and daughter chromosome decatenation.
Hiasa
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Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Marians
K J
KJ
D004261:DNA Replication; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004269:DNA, Bacterial / Q000096:biosynthesis* / Q000378:metabolism; D007700:Kinetics
D004269:DNA, Bacterial; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II