Topoisomerase IV can functionally replace all type 1A topoisomerases in Bacillus subtilis

• Published in: Nucleic acids research 2019-06, Vol.47 (10), p.5231-5242
• Main Authors: Reuß, Daniel R, Faßhauer, Patrick, Mroch, Philipp Joel, Ul-Haq, Inam, Koo, Byoung-Mo, Pöhlein, Anja, Gross, Carol A, Daniel, Rolf, Brantl, Sabine, Stülke, Jörg
• Format: Article
• Language: English
• Subjects: Bacillus subtilis - enzymology; Bacillus subtilis - genetics; Bacterial Proteins - metabolism; Chromosomes, Bacterial; DNA Replication; DNA Topoisomerase IV - metabolism; DNA Topoisomerases, Type I - metabolism; DNA, Bacterial - genetics; DNA, Superhelical - genetics; DNA-Directed RNA Polymerases - metabolism; Escherichia coli - genetics; Escherichia coli Proteins - metabolism; Genome, Bacterial; Molecular Biology; Mutation; Phenotype; Point Mutation; Promoter Regions, Genetic
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/gkz260

DNA topoisomerases play essential roles in chromosome organization and replication. Most bacteria possess multiple topoisomerases which have specialized functions in the control of DNA supercoiling or in DNA catenation/decatenation during recombination and chromosome segregation. DNA topoisomerase I is required for the relaxation of negatively supercoiled DNA behind the transcribing RNA polymerase. Conflicting results have been reported on the essentiality of the topA gene encoding topoisomerase I in the model bacterium Bacillus subtilis. In this work, we have studied the requirement for topoisomerase I in B. subtilis. All stable topA mutants carried different chromosomal amplifications of the genomic region encompassing the parEC operon encoding topoisomerase IV. Using a fluorescent amplification reporter system we observed that each individual topA mutant had acquired such an amplification. Eventually, the amplifications were replaced by a point mutation in the parEC promoter region which resulted in a fivefold increase of parEC expression. In this strain both type I topoisomerases, encoded by topA and topB, were dispensable. Our results demonstrate that topoisomerase IV at increased expression is necessary and sufficient to take over the function of type 1A topoisomerases.