Gene Symbol: topA
Description: DNA topoisomerase I, omega subunit
Alias: ECK1268, JW1266, asuA?, supX
Species: Escherichia coli str. K-12 substr. MG1655

Top Publications

  1. Reddy M, Gowrishankar J. Characterization of the uup locus and its role in transposon excisions and tandem repeat deletions in Escherichia coli. J Bacteriol. 2000;182:1978-86 pubmed
    ..of precise excision of Tn10 are divisible into two categories, depending upon whether they did (uup, ssb, polA, and topA) or did not (mutHLS, dam, and uvrD) also increase precise excision frequency of the mini-Tn10 derivatives...
  2. Snoep J, van der Weijden C, Andersen H, Westerhoff H, Jensen P. DNA supercoiling in Escherichia coli is under tight and subtle homeostatic control, involving gene-expression and metabolic regulation of both topoisomerase I and DNA gyrase. Eur J Biochem. 2002;269:1662-9 pubmed
    ..3% change of DNA supercoiling only. We conclude that the homeostatic regulation of the nonequilibrium DNA structure in wild-type Escherichia coli is almost complete and subtle (i.e. involving at least three regulatory mechanisms). ..
  3. Qi H, Menzel R, Tse Dinh Y. Effect of the deletion of the sigma 32-dependent promoter (P1) of the Escherichia coli topoisomerase I gene on thermotolerance. Mol Microbiol. 1996;21:703-11 pubmed
    ..The P1 promoter of topA has previously been shown to be a delta 32-dependent heat-shock promoter...
  4. Yigit H, Reznikoff W. Escherichia coli DNA topoisomerase I copurifies with Tn5 transposase, and Tn5 transposase inhibits topoisomerase I. J Bacteriol. 1999;181:3185-92 pubmed
    ..For RNA polymerase, reduced copurification with Tnp is observed in extracts from a topA mutant strain, suggesting that RNA polymerase interacts with Topo I and not Tnp.
  5. Cheng B, Zhu C, Ji C, Ahumada A, Tse Dinh Y. Direct interaction between Escherichia coli RNA polymerase and the zinc ribbon domains of DNA topoisomerase I. J Biol Chem. 2003;278:30705-10 pubmed
    Escherichia coli DNA topoisomerase I (encoded by the topA gene) is important for maintaining steady-state DNA supercoiling and has been shown to influence vital cellular processes including transcription...
  6. Perry K, MONDRAGON A. Structure of a complex between E. coli DNA topoisomerase I and single-stranded DNA. Structure. 2003;11:1349-58 pubmed
    ..The structure helps clarify the temporal sequence of conformational events, starting from an initial empty enzyme and proceeding to a ssDNA-occupied and catalytically competent active site. ..
  7. Sternglanz R, DiNardo S, Voelkel K, Nishimura Y, Hirota Y, Becherer K, et al. Mutations in the gene coding for Escherichia coli DNA topoisomerase I affect transcription and transposition. Proc Natl Acad Sci U S A. 1981;78:2747-51 pubmed
    ..Based on the studies of the E. coli top mutants, it appears that the supX gene, which was originally studied in Salmonella typhimurium [Dubnau, E. & Margolin, P. (1972) Mol. Gen. Genet...
  8. Masse E, Drolet M. Relaxation of transcription-induced negative supercoiling is an essential function of Escherichia coli DNA topoisomerase I. J Biol Chem. 1999;274:16654-8 pubmed
    ..whether topoisomerase I is essential for controlling global or local DNA supercoiling, we have prepared a set of topA null mutant strains in combination with different plasmid DNAs...
  9. Cheng B, Liu I, Tse Dinh Y. Compounds with antibacterial activity that enhance DNA cleavage by bacterial DNA topoisomerase I. J Antimicrob Chemother. 2007;59:640-5 pubmed
    ..Small molecules that can enhance the DNA cleavage activity of type IA DNA topoisomerase can be identified and may provide leads for development of novel antibacterial compounds. ..

More Information


  1. Lynn R, Wang J. Peptide sequencing and site-directed mutagenesis identify tyrosine-319 as the active site tyrosine of Escherichia coli DNA topoisomerase I. Proteins. 1989;6:231-9 pubmed
    ..The structure of the enzyme and its catalysis of DNA strand breakage, passage, and rejoining are discussed in terms of the available information. ..
  2. Zhu Q, Pongpech P, DiGate R. Type I topoisomerase activity is required for proper chromosomal segregation in Escherichia coli. Proc Natl Acad Sci U S A. 2001;98:9766-71 pubmed
    ..Cells possessing a deletion of the gene encoding Topo I (topA) are only viable in the presence of an additional compensatory mutation...
  3. Lima C, Wang J, Mondragon A. Crystallization of a 67 kDa fragment of Escherichia coli DNA topoisomerase I. J Mol Biol. 1993;232:1213-6 pubmed
    ..A complete native data set and two derivative data sets have been collected. A multiple isomorphous replacement map to 3 A resolution shows clear secondary structural elements. Final structure determination is in progress. ..
  4. Tse Dinh Y. Increased sensitivity to oxidative challenges associated with topA deletion in Escherichia coli. J Bacteriol. 2000;182:829-32 pubmed
    Deletion of topA in Escherichia coli was found to result in a higher level of killing after treatment with either hydrogen peroxide or N-ethylmaleimide. This effect on oxidative challenge response represents a new role for E...
  5. DiNardo S, Voelkel K, Sternglanz R, Reynolds A, Wright A. Escherichia coli DNA topoisomerase I mutants have compensatory mutations in DNA gyrase genes. Cell. 1982;31:43-51 pubmed
    ..An excess of negative supercoils due to an absence of topoisomerase I is deleterious to the cell, but a moderate gyrase deficiency is not harmful. ..
  6. Perry K, MONDRAGON A. Biochemical characterization of an invariant histidine involved in Escherichia coli DNA topoisomerase I catalysis. J Biol Chem. 2002;277:13237-45 pubmed
    ..These observations indicate that His-365 participates in DNA binding and is responsible for optimal catalysis at physiological pH. ..
  7. Cheng B, Sorokin E, Tse Dinh Y. Mutation adjacent to the active site tyrosine can enhance DNA cleavage and cell killing by the TOPRIM Gly to Ser mutant of bacterial topoisomerase I. Nucleic Acids Res. 2008;36:1017-25 pubmed
  8. Drolet M. Growth inhibition mediated by excess negative supercoiling: the interplay between transcription elongation, R-loop formation and DNA topology. Mol Microbiol. 2006;59:723-30 pubmed
    ..Growth inhibition mediated by excess negative supercoiling might be related to this interplay between transcription elongation and supercoiling. ..
  9. Weinstein Fischer D, Elgrably Weiss M, Altuvia S. Escherichia coli response to hydrogen peroxide: a role for DNA supercoiling, topoisomerase I and Fis. Mol Microbiol. 2000;35:1413-20 pubmed
    ..We also report that hydrogen peroxide activates topA P1 promoter expression. The peroxide-dependent topA P1 activation is independent of oxyR, but is mediated by Fis...
  10. Tse Dinh Y, Qi H, Menzel R. DNA supercoiling and bacterial adaptation: thermotolerance and thermoresistance. Trends Microbiol. 1997;5:323-6 pubmed
    ..This role in heat shock has been elucidated by genetic studies on the Escherichia coli topA gene and its sigma 32-dependent promoter, P1...
  11. Tse Dinh Y, Beran R. Multiple promoters for transcription of the Escherichia coli DNA topoisomerase I gene and their regulation by DNA supercoiling. J Mol Biol. 1988;202:735-42 pubmed
    ..are four transcriptional promoters present in the 5' control region of the Escherichia coli DNA topoisomerase I (topA) gene...
  12. Weinstein Fischer D, Altuvia S. Differential regulation of Escherichia coli topoisomerase I by Fis. Mol Microbiol. 2007;63:1131-44 pubmed
    We previously reported that the P1 promoter of topA encoding topoisomerase I of Escherichia coli is activated in response to oxidative stress, in a Fis-dependent manner...
  13. Tse Dinh Y. Zinc (II) coordination in Escherichia coli DNA topoisomerase I is required for cleavable complex formation with DNA. J Biol Chem. 1991;266:14317-20 pubmed
    ..It is proposed that zinc(II) coordination in E. coli DNA topoisomerase I is required for the transition of the noncovalent complex with DNA to the cleavable state. ..
  14. Wang Y, Lynch A, Chen S, Wang J. On the molecular basis of the thermal sensitivity of an Escherichia coli topA mutant. J Biol Chem. 2002;277:1203-9 pubmed
    Studies of two temperature-sensitive Escherichia coli topA strains AS17 and BR83, both of which were supposed to carry a topA amber mutation and a temperature-sensitive supD43,74 amber-suppressor, led to conflicting results regarding the ..
  15. Drlica K. Control of bacterial DNA supercoiling. Mol Microbiol. 1992;6:425-33 pubmed
    ..However, a steady-state change in supercoiling caused by mutation of topA does alter both tension and restrained supercoils...
  16. Tse Dinh Y, Beran Steed R. Escherichia coli DNA topoisomerase I is a zinc metalloprotein with three repetitive zinc-binding domains. J Biol Chem. 1988;263:15857-9 pubmed
    ..Zinc ions are needed for full recovery of enzyme activity when the cysteine modification is reversed. Comparison with the zinc-binding domains of the sequence-specific DNA-binding proteins shows significant differences. ..
  17. Lima C, Wang J, Mondragon A. Three-dimensional structure of the 67K N-terminal fragment of E. coli DNA topoisomerase I. Nature. 1994;367:138-46 pubmed
    ..The structure suggests a plausible mechanism by which E. coli DNA topoisomerase I and other members of the same DNA topoisomerase subfamily could catalyse the passage of one DNA strand through a transient break in another strand. ..
  18. Cheng B, Feng J, Mulay V, Gadgil S, Tse Dinh Y. Site-directed mutagenesis of residues involved in G Strand DNA binding by Escherichia coli DNA topoisomerase I. J Biol Chem. 2004;279:39207-13 pubmed
    ..Mutation of Ser-192 did not affect DNA binding and cleavage but nevertheless decreased the overall rate of relaxation of supercoiled DNA probably because of its participation in a later step of the reaction pathway. ..
  19. Masse E, Drolet M. R-loop-dependent hypernegative supercoiling in Escherichia coli topA mutants preferentially occurs at low temperatures and correlates with growth inhibition. J Mol Biol. 1999;294:321-32 pubmed
    We have recently presented evidence that inhibitory R-loops form during transcription in topA null mutants when the nascent RNA anneals with the template DNA strand behind the moving RNA polymerase...
  20. Sutherland J, Cheng B, Liu I, Tse Dinh Y. SOS induction by stabilized topoisomerase IA cleavage complex occurs via the RecBCD pathway. J Bacteriol. 2008;190:3399-403 pubmed publisher
    ..The single-stranded break associated with mutant topoisomerase I cleavage complex is converted to double-stranded break, which then is processed by the RecBCD pathway, followed by association of RecA with the single-stranded DNA. ..
  21. Zumstein L, Wang J. Probing the structural domains and function in vivo of Escherichia coli DNA topoisomerase I by mutagenesis. J Mol Biol. 1986;191:333-40 pubmed
    Insertion and deletion mutagenesis within the gene topA of Escherichia coli encoding DNA topoisomerase I was carried out to test the existence of subdomains in the enzyme and the relationship between the slow-growth topA- phenotype and ..
  22. Yu L, Zhu C, Tse Dinh Y, Fesik S. Solution structure of the C-terminal single-stranded DNA-binding domain of Escherichia coli topoisomerase I. Biochemistry. 1995;34:7622-8 pubmed
    ..The binding site consists of a beta-sheet containing positively charged and aromatic amino acids and, in spite of its different structure, is similar to that found in other proteins that bind single-stranded oligonucleotides. ..
  23. Grompone G, Ehrlich S, Michel B. Replication restart in gyrB Escherichia coli mutants. Mol Microbiol. 2003;48:845-54 pubmed
  24. Qi H, Menzel R, Tse Dinh Y. Regulation of Escherichia coli topA gene transcription: involvement of a sigmaS-dependent promoter. J Mol Biol. 1997;267:481-9 pubmed
    To investigate the regulation of Escherichia coli topA gene transcription, primer extension was employed to determine the transcription initiation sites from the chromosomal topA gene...
  25. Feinberg H, Lima C, Mondragon A. Conformational changes in E. coli DNA topoisomerase I. Nat Struct Biol. 1999;6:918-22 pubmed
    ..The fragment is composed of two domains, and while the domains themselves remain largely unchanged, their relative arrangement can change dramatically. ..
  26. Cheng B, Shukla S, Vasunilashorn S, Mukhopadhyay S, Tse Dinh Y. Bacterial cell killing mediated by topoisomerase I DNA cleavage activity. J Biol Chem. 2005;280:38489-95 pubmed
    ..Small molecules that induce similar perturbation in the enzyme-DNA complex should be candidates as leads for novel antibacterial agents. ..
  27. Mizushima T, Natori S, Sekimizu K. Inhibition of Escherichia coli DNA topoisomerase I activity by phospholipids. Biochem J. 1992;285 ( Pt 2):503-6 pubmed
    ..Treatment of E. coli cells with chlorpromazine resulted in relaxation of plasmid DNA. This DNA relaxation was not observed in a topA mutant, suggesting that this relaxation by chlorpromazine in vivo is catalysed by topoisomerase I.
  28. Feinberg H, Changela A, Mondragon A. Protein-nucleotide interactions in E. coli DNA topoisomerase I. Nat Struct Biol. 1999;6:961-8 pubmed
    ..The positions of these sites allow us to identify different DNA binding regions and to understand their possible roles in the catalytic cycle. ..
  29. Tse Dinh Y, Wang J. Complete nucleotide sequence of the topA gene encoding Escherichia coli DNA topoisomerase I. J Mol Biol. 1986;191:321-31 pubmed
    The nucleotide sequence of a 4071 base-pair long segment containing the gene topA encoding Escherichia coli DNA topoisomerase I and its flanking regions has been determined...
  30. Stupina V, Wang J. Viability of Escherichia coli topA mutants lacking DNA topoisomerase I. J Biol Chem. 2005;280:355-60 pubmed
    The viability of the topA mutants lacking DNA topoisomerase I was thought to depend on the presence of compensatory mutations in Escherichia coli but not Salmonella typhimurium or Shigella flexneri...
  31. Pruss G, Manes S, Drlica K. Escherichia coli DNA topoisomerase I mutants: increased supercoiling is corrected by mutations near gyrase genes. Cell. 1982;31:35-42 pubmed
  32. Qi H, Menzel R, Tse Dinh Y. Increased thermosensitivity associated with topoisomerase I deletion and promoter mutations in Escherichia coli. FEMS Microbiol Lett. 1999;178:141-6 pubmed
    An Escherichia coli mutant with three of the promoters for the topoisomerase I gene (topA) deleted, such that only the sigma 32-dependent promoter (P1) remained, had a decreased level of topoisomerase I at 30 degrees C and showed ..
  33. Zechiedrich E, Khodursky A, Bachellier S, Schneider R, Chen D, Lilley D, et al. Roles of topoisomerases in maintaining steady-state DNA supercoiling in Escherichia coli. J Biol Chem. 2000;275:8103-13 pubmed
    ..09), greatly stimulating transcription from the supercoiling sensitive leu-500 promoter and increasing the number of supercoils trapped by lambda integrase site-specific recombination. ..
  34. Trucksis M, Golub E, Zabel D, Depew R. Escherichia coli and Salmonella typhimurium supX genes specify deoxyribonucleic acid topoisomerase I. J Bacteriol. 1981;147:679-81 pubmed
    Mutations of the Escherichia coli or Salmonella typhimurium supX genes eliminated deoxyribonucleic acid topoisomerase I. Suppression of a supX amber mutation partially restored the topoisomerase...
  35. Zheng Y, Roberts R, Kasif S. Segmentally variable genes: a new perspective on adaptation. PLoS Biol. 2004;2:E81 pubmed
    ..Discerning their function and identifying their binding partners may offer biologists new insights into the basic mechanisms of adaptation, context-dependent evolution, and the interaction between microbes and their environment. ..
  36. Majchrzak M, Bowater R, Staczek P, Parniewski P. SOS repair and DNA supercoiling influence the genetic stability of DNA triplet repeats in Escherichia coli. J Mol Biol. 2006;364:612-24 pubmed
    ..These observations suggest a link between the induction of bacterial SOS repair, changes in DNA topology and the mechanisms leading to genetic instability of repetitive DNA sequences. ..
  37. Raji A, Zabel D, Laufer C, Depew R. Genetic analysis of mutations that compensate for loss of Escherichia coli DNA topoisomerase I. J Bacteriol. 1985;162:1173-9 pubmed
    A transposon Tn10 insertion in topA, the structural gene of Escherichia coli DNA topoisomerase I, behaves as an excluded marker in genetic crosses with many strains of E. coli...
  38. Trucksis M, Depew R. Identification and localization of a gene that specifies production of Escherichia coli DNA topoisomerase I. Proc Natl Acad Sci U S A. 1981;78:2164-8 pubmed
    ..Deletions that eliminated topA also eliminated the supX gene. We suggest that topA is the structural gene of E. coli DNA topoisomerase I and that topA is identical to supX. ..
  39. Terekhova K, Gunn K, Marko J, MONDRAGON A. Bacterial topoisomerase I and topoisomerase III relax supercoiled DNA via distinct pathways. Nucleic Acids Res. 2012;40:10432-40 pubmed publisher
    ..The combination of these properties results in Topo I having an overall faster total relaxation rate, even though the relaxation rate during a run for Topo III is much faster. ..
  40. Valjavec Gratian M, Henderson T, Hill T. Tus-mediated arrest of DNA replication in Escherichia coli is modulated by DNA supercoiling. Mol Microbiol. 2005;58:758-73 pubmed
    ..Resistance to tus expression mapped to a mutation in the stop codon of the topA gene (topA869), generating an elongated topoisomerase I protein with a marked reduction in activity...
  41. Banda S, Tiwari P, Darici Y, Tse Dinh Y. Investigating direct interaction between Escherichia coli topoisomerase I and RecA. Gene. 2016;585:65-70 pubmed publisher
    ..Our results from pull-down assays showed that ATP, although not required, enhances the RecA-EcTOP1 interaction. We propose that E. coli RecA physically interacts with topoisomerase I to modulate the chromosomal DNA supercoiling. ..
  42. Bjornsti M, Wang J. Expression of yeast DNA topoisomerase I can complement a conditional-lethal DNA topoisomerase I mutation in Escherichia coli. Proc Natl Acad Sci U S A. 1987;84:8971-5 pubmed
    ..coli topA mutant...
  43. Ostrowski J, Jagura Burdzy G, Kredich N. DNA sequences of the cysB regions of Salmonella typhimurium and Escherichia coli. J Biol Chem. 1987;262:5999-6005 pubmed
    ..Sequences upstream to cysB contain open reading frames which represent the carboxyl-terminal end of the topA gene product, DNA topoisomerase I...
  44. Heddle J, Lu T, Zhao X, Drlica K, Maxwell A. gyrB-225, a mutation of DNA gyrase that compensates for topoisomerase I deficiency: investigation of its low activity and quinolone hypersensitivity. J Mol Biol. 2001;309:1219-31 pubmed
    ..In cells containing a deletion of topA (the gene encoding DNA topoisomerase I) a compensatory mutation is found in gyrB...
  45. Ogata Y, Mizushima T, Kataoka K, Miki T, Sekimizu K. Identification of DNA topoisomerases involved in immediate and transient DNA relaxation induced by heat shock in Escherichia coli. Mol Gen Genet. 1994;244:451-5 pubmed
    ..Neither introduction of a topA deletion mutation nor treatment of cells with DNA gyrase inhibitors affected the DNA relaxation induced by heat ..
  46. Louarn J, Bouche J, Patte J, Louarn J. Genetic inactivation of topoisomerase I suppresses a defect in initiation of chromosome replication in Escherichia coli. Mol Gen Genet. 1984;195:170-4 pubmed
    ..Escherichia coli K12 harboring simultaneously the temperature-sensitive dnaA46 mutation and a deletion of the trp-topA-cysB region plates with the same full efficiency at 30 degrees C and 42 degrees C...
  47. DasGupta S, Maisnier Patin S, Nordstrom K. New genes with old modus operandi. The connection between supercoiling and partitioning of DNA in Escherichia coli. EMBO Rep. 2000;1:323-7 pubmed
    ..Thus, genes involved in chromosome topology, once set aside as 'red herrings' in the search for 'true' partition functions, are again recognized as being important for chromosome partitioning in E. coli. ..
  48. DiGate R. Overexpression and purification of Escherichia coli DNA topoisomerase III. Methods Mol Biol. 1999;94:153-62 pubmed
  49. Stockum A, Lloyd R, Rudolph C. On the viability of Escherichia coli cells lacking DNA topoisomerase I. BMC Microbiol. 2012;12:26 pubmed publisher
    ..In Escherichia coli there is conflicting data about viability of ?topA cells lacking topoisomerase I. In this study we sought to clarify whether E...
  50. Oram M, Fisher L. An Escherichia coli DNA topoisomerase I mutant has a compensatory mutation that alters two residues between functional domains of the DNA gyrase A protein. J Bacteriol. 1992;174:4175-8 pubmed
    ..coli DM800 (in gyrase B protein) suggests that these compensatory mutations may reduce DNA supercoiling activity by altering allosteric interactions in the gyrase complex. ..
  51. Shishido K, Komiyama N, Ikawa S. Increased production of a knotted form of plasmid pBR322 DNA in Escherichia coli DNA topoisomerase mutants. J Mol Biol. 1987;195:215-8 pubmed
    Plasmid pBR322 prepared from Escherichia coli strains carrying deletion of the DNA topoisomerase I gene (delta topA) with a compensatory mutation of the DNA gyrase gene (gyrA or gyrB) and from their TopA+ transductants was analyzed by ..
  52. Baaklini I, Usongo V, Nolent F, Sanscartier P, Hraiky C, Drlica K, et al. Hypernegative supercoiling inhibits growth by causing RNA degradation. J Bacteriol. 2008;190:7346-56 pubmed publisher
    Transcription-induced hypernegative supercoiling is a hallmark of Escherichia coli topoisomerase I (topA) mutants. However, its physiological significance has remained unclear...
  53. Dressler D, Potter H. Molecular mechanisms in genetic recombination. Annu Rev Biochem. 1982;51:727-61 pubmed
  54. Dubnau E, Margolin P. Suppression of promoter mutations by the pleiotropic supx mutations. Mol Gen Genet. 1972;117:91-112 pubmed
  55. Viard T, Cossard R, Duguet M, de La Tour C. Thermotoga maritima-Escherichia coli chimeric topoisomerases. Answers about involvement of the carboxyl-terminal domain in DNA topoisomerase I-mediated catalysis. J Biol Chem. 2004;279:30073-80 pubmed publisher
  56. Yang J, Annamalai T, Cheng B, Banda S, Tyagi R, Tse Dinh Y. Antimicrobial Susceptibility and SOS-Dependent Increase in Mutation Frequency Are Impacted by Escherichia coli Topoisomerase I C-Terminal Point Mutation. Antimicrob Agents Chemother. 2015;59:6195-202 pubmed publisher, Escherichia coli with a topA66 single nucleotide deletion mutation, which results in a frameshift in the TopA CTD, was shown to exhibit increased sensitivity to trimethoprim and quinolone antimicrobials...
  57. Zhi X, Leng F. Dependence of transcription-coupled DNA supercoiling on promoter strength in Escherichia coli topoisomerase I deficient strains. Gene. 2013;514:82-90 pubmed publisher
    ..In Escherichia coli topA strains, DNA gyrase selectively converts the positively supercoiled domain into negative supercoils to produce ..
  58. Cheng B, Rui S, Ji C, Gong V, Van Dyk T, Drolet M, et al. RNase H overproduction allows the expression of stress-induced genes in the absence of topoisomerase I. FEMS Microbiol Lett. 2003;221:237-42 pubmed
    ..Topoisomerase I is likely required during stress response for preventing accumulation of transcription-driven hypernegative supercoiling and R-loop formation at induced stress genes loci. ..
  59. Lenny A, Margolin P. Locations of the opp and supX genes of Salmonella typhimurium and Escherichia coli. J Bacteriol. 1980;143:747-52 pubmed
    The chromosomal locations of the supX and opp loci of Salmonella typhimurium LT2 and Escherichia coli K-12 were identified and found to result in the same gene sequence in both species, namely, pyrF-cysB-supX-trpPOLEDCBA-tonB(chr)-opp...
  60. Strahs D, Zhu C, Cheng B, Chen J, Tse Dinh Y. Experimental and computational investigations of Ser10 and Lys13 in the binding and cleavage of DNA substrates by Escherichia coli DNA topoisomerase I. Nucleic Acids Res. 2006;34:1785-97 pubmed
  61. Liu I, Annamalai T, Sutherland J, Tse Dinh Y. Hydroxyl radicals are involved in cell killing by the bacterial topoisomerase I cleavage complex. J Bacteriol. 2009;191:5315-9 pubmed publisher
    ..The presence of the Fe(2+) chelator 2,2'-dipyridyl and an iscS mutation affecting Fe-S cluster formation protect against topoisomerase I cleavage complex-mediated cell killing...
  62. Schmidt K, Reimers J, Wright B. The effect of promoter strength, supercoiling and secondary structure on mutation rates in Escherichia coli. Mol Microbiol. 2006;60:1251-61 pubmed
    ..The cat mutants had higher reversion rates in a topA mutant strain with increased negative supercoiling compared with wild-type levels, and the cat reversion rates were ..
  63. Sun Q, Margolin W. Effects of perturbing nucleoid structure on nucleoid occlusion-mediated toporegulation of FtsZ ring assembly. J Bacteriol. 2004;186:3951-9 pubmed
    ..We found that NO was mostly normal in cells with inactivated DNA gyrase or in mukB-null mutants lacking topA, although some suppression of NO was evident in the latter case...
  64. Tse Dinh Y. Bacterial topoisomerase I as a target for discovery of antibacterial compounds. Nucleic Acids Res. 2009;37:731-7 pubmed publisher
    ..Topoisomerase I targeting poisons may be particularly effective when the bacterial pathogen is responding to host defense, or in the presence of other antibiotics that induce the bacterial stress response. ..
  65. Wang J, Becherer K. Cloning of the gene topA encoding for DNA topoisomerase I and the physical mapping of the cysB-topA-trp region of Escherichia coli. Nucleic Acids Res. 1983;11:1773-90 pubmed
    The gene topA of Escherichia coli that encodes for DNA topoisomerase I has been cloned by a combination of genetic and radioimmunal screening. The gene has been mapped to be within a 3.4 Kb segment of the bacterial genome...
  66. Olsson J, Nordström K, Hjort K, Dasgupta S. Eclipse-synchrony relationship in Escherichia coli strains with mutations affecting sequestration, initiation of replication and superhelicity of the bacterial chromosome. J Mol Biol. 2003;334:919-31 pubmed
    ..6 for the wild-type E.coli K12 to 0.1 for strains with mutations in seqA, dam, dnaA, topA and gyr genes (all of which have been shown to cause asynchrony) and their various combinations...