The role of topoisomerase IV in partitioning bacterial replicons and the structure of catenated intermediates in DNA replication

The bacterial nucleoid: A highly organized and dynamic structure

“…This intermolecular link must be resolved by topoisomerase IV before closure of the division septum can occur [Adams et al, 1992;Peng and Marians, 1993]. The importance of this reaction is underscored by the fact that loss of decatenation activity causes filamentation, accumulation of anucleate cells, and cell death in E. coli and Salmonella typhimurium [Kato et al, 1988[Kato et al, , 1990Springer and Schmid, 1993].…”

The probabilities of supercoil removal and decatenation by yeast DNA topoisomerase II

“…In bacteria such as Escherichia coli and Salmonella typhimurium, there are two distinct type II DNA topoisomerases: gyrase (DNA topoisomerase II) and DNA topoisomerase IV (Kato et al 1990;Luttinger et al 1991). Inside a cell or in reconstituted DNA replication systems, the former appears to be mainly involved in the intramolecular reaction of removing positive supercoils or introducing negative ones, while the latter mainly in decatenation of intertwined replicative products (Adams et al 1992;Hiasa & Marians 1994). Several possible explanations were suggested to account for this division of labour: the enzymes might be differently compartmentalized inside a cell or along a replicating DNA, and the catenated replicative products might have structural characteristics that make them the preferred substrates of DNA topoisomerase IV but not gyrase (Adams et al 1992).…”

“…Inside a cell or in reconstituted DNA replication systems, the former appears to be mainly involved in the intramolecular reaction of removing positive supercoils or introducing negative ones, while the latter mainly in decatenation of intertwined replicative products (Adams et al 1992;Hiasa & Marians 1994). Several possible explanations were suggested to account for this division of labour: the enzymes might be differently compartmentalized inside a cell or along a replicating DNA, and the catenated replicative products might have structural characteristics that make them the preferred substrates of DNA topoisomerase IV but not gyrase (Adams et al 1992). In the budding yeast Saccharomyces cerevisiae, only one type II enzyme, yeast DNA topoisomerase II, is known (Goto & Wang 1984).…”

Comparison of inhibition of Escherichia coli topoisomerase IV by quinolones with DNA gyrase inhibition

“…Among these enzymes, topoisomerases I, II, and IV are implicated in the control of the intracellular supercoiling density of chromosomal or plasmid DNA, affecting the efficacy of DNA replication and transcription (4, 6-8, 20, 24, 29, 36, 37). In addition, some topoisomerases are required for the segregation of daughter chromosomes or plasmid DNA (1,21,35,40). Although all of these topoisomerases are capable of changing the topology of DNA by a cleaving and rejoining step, each enzyme appears to possess a favored reaction in vitro.…”

“…Of the type II topoisomerases, DNA gyrase is unique in its ability to supercoil relaxed DNA in the presence of ATP (9) and topoisomerase IV decatenates catenated DNA in vitro (28). Furthermore, in vitro only DNA gyrase and topoisomerase IV can segregate intact catenated DNA in the presence of ATP (1,19,23,27,35); however, recent work has suggested that DNA gyrase may not act as a decatenating enzyme in bacterial cells (1,11). The type II topoisomerases are thought to be essential for bacterial growth because of inducible lethality in temperature-sensitive mutants (16,17).…”