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Gene Review

TOP3  -  DNA topoisomerase 3

Saccharomyces cerevisiae S288c

Synonyms: DNA topoisomerase III, EDR1, L8083.3, YLR234W
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Disease relevance of TOP3


High impact information on TOP3

  • Srs2 and Sgs1-Top3 suppress crossovers during double-strand break repair in yeast [4].
  • Finally, top3 and top3 sgs1 mutants accumulate the same structures as sgs1 cells [5].
  • On the other hand, Sgs1p's helicase activity is required together with Top3p and the strand-exchange factor Rad51p, to help stabilise DNA polymerase epsilon at stalled replication forks [6].
  • Yeast cells mutant for TOP3, the gene encoding the evolutionary conserved type I-5' topoisomerase, display a wide range of phenotypes including altered cell cycle, hyper-recombination, abnormal gene expression, poor mating, chromosome instability and absence of sporulation [7].
  • In this report, an analysis of the role of TOP3 in the meiotic process indicates that top3Delta mutants enter meiosis and complete the initial steps of recombination [7].

Biological context of TOP3

  • Based on synthetic phenotypes, the intra-S-phase checkpoint, the SRS2 inhibitor of recombination, the SGS1/TOP3 replication fork restart pathway, and the MRE11/RAD50/XRS2 (MRX) complex were critical for viability of rrm3 cells [8].
  • Genome stability requires a set of RecQ-Top3 DNA helicase-topoisomerase complexes whose sole budding yeast homolog is encoded by SGS1-TOP3 [9].
  • Saccharomyces cerevisiae cells that are mutated at TOP3, a gene that encodes a protein homologous to bacterial type I topoisomerases, have a variety of defects, including reduced growth rate, altered gene expression, blocked sporulation, and elevated rates of mitotic recombination at several loci [10].
  • In budding yeast, loss of topoisomerase III, encoded by the TOP3 gene, leads to a genomic instability phenotype that includes slow growth, hyper-sensitivity to genotoxic agents, mitotic hyper-recombination, increased chromosome missegregation, and meiotic failure [11].
  • On their own, mutations in RMI1 result in phenotypes that mimic those of sgs1 or top3 strains including slow growth, hyperrecombination, DNA damage sensitivity, and reduced sporulation [9].

Associations of TOP3 with chemical compounds

  • In this study, we found that several amino acids residues in the N-terminal region of Sgs1 between residues 4 and 33 were responsible for binding to Top3 and essential for complementing the sensitivity to MMS of sgsl cells [12].
  • Consistent with these physical data, we find that mutant phenotypes caused by a point mutation or small deletions in the Sgs1 NH(2) terminus can be suppressed by Top3 overexpression [13].

Physical interactions of TOP3

  • The meiotic block is also partially suppressed by a deletion of SGS1, a gene encoding a helicase that interacts with Top3 [7].

Other interactions of TOP3

  • We propose that the DNA binding specificity of Rmi1 plays a role in targeting Sgs1-Top3 to appropriate substrates [9].
  • None of these genes is required for viability and all SLX null mutations are synthetically lethal with mutations in TOP3, encoding the SGS1-interacting DNA topoisomerase [14].
  • We present a model wherein Rad51 helps recruit Sgs1-Top3 to sites of replicative damage [11].
  • These results suggest that a RAD1-dependent function is involved in the processing of damaged DNA that results from the loss of Top3 activity, targeting such DNA for repair by recombination [10].
  • The rate of ectopic recombination between two unlinked, homologous loci, SAM1 and SAM2, is sixfold higher in cells containing a top3 null mutation than in wild-type cells [10].

Analytical, diagnostic and therapeutic context of TOP3


  1. Topoisomerase III acts upstream of Rad53p in the S-phase DNA damage checkpoint. Chakraverty, R.K., Kearsey, J.M., Oakley, T.J., Grenon, M., de La Torre Ruiz, M.A., Lowndes, N.F., Hickson, I.D. Mol. Cell. Biol. (2001) [Pubmed]
  2. Identification of the yeast TOP3 gene product as a single strand-specific DNA topoisomerase. Kim, R.A., Wang, J.C. J. Biol. Chem. (1992) [Pubmed]
  3. The possible roles of the DNA helicase and C-terminal domains in RECQ5/QE: complementation study in yeast. Nakayama, M., Kawasaki, K., Matsumoto, K., Shibata, T. DNA Repair (Amst.) (2004) [Pubmed]
  4. Srs2 and Sgs1-Top3 suppress crossovers during double-strand break repair in yeast. Ira, G., Malkova, A., Liberi, G., Foiani, M., Haber, J.E. Cell (2003) [Pubmed]
  5. Rad51-dependent DNA structures accumulate at damaged replication forks in sgs1 mutants defective in the yeast ortholog of BLM RecQ helicase. Liberi, G., Maffioletti, G., Lucca, C., Chiolo, I., Baryshnikova, A., Cotta-Ramusino, C., Lopes, M., Pellicioli, A., Haber, J.E., Foiani, M. Genes Dev. (2005) [Pubmed]
  6. Mechanistically distinct roles for Sgs1p in checkpoint activation and replication fork maintenance. Bjergbaek, L., Cobb, J.A., Tsai-Pflugfelder, M., Gasser, S.M. EMBO J. (2005) [Pubmed]
  7. The essential role of yeast topoisomerase III in meiosis depends on recombination. Gangloff, S., de Massy, B., Arthur, L., Rothstein, R., Fabre, F. EMBO J. (1999) [Pubmed]
  8. Saccharomyces cerevisiae Rrm3p DNA helicase promotes genome integrity by preventing replication fork stalling: viability of rrm3 cells requires the intra-S-phase checkpoint and fork restart activities. Torres, J.Z., Schnakenberg, S.L., Zakian, V.A. Mol. Cell. Biol. (2004) [Pubmed]
  9. Yeast Rmi1/Nce4 controls genome stability as a subunit of the Sgs1-Top3 complex. Mullen, J.R., Nallaseth, F.S., Lan, Y.Q., Slagle, C.E., Brill, S.J. Mol. Cell. Biol. (2005) [Pubmed]
  10. Genome rearrangement in top3 mutants of Saccharomyces cerevisiae requires a functional RAD1 excision repair gene. Bailis, A.M., Arthur, L., Rothstein, R. Mol. Cell. Biol. (1992) [Pubmed]
  11. Mutations in homologous recombination genes rescue top3 slow growth in Saccharomyces cerevisiae. Shor, E., Gangloff, S., Wagner, M., Weinstein, J., Price, G., Rothstein, R. Genetics (2002) [Pubmed]
  12. Functional and physical interaction between Sgs1 and Top3 and Sgs1-independent function of Top3 in DNA recombination repair. Onodera, R., Seki, M., Ui, A., Satoh, Y., Miyajima, A., Onoda, F., Enomoto, T. Genes Genet. Syst. (2002) [Pubmed]
  13. Mapping the DNA topoisomerase III binding domain of the Sgs1 DNA helicase. Fricke, W.M., Kaliraman, V., Brill, S.J. J. Biol. Chem. (2001) [Pubmed]
  14. Requirement for three novel protein complexes in the absence of the Sgs1 DNA helicase in Saccharomyces cerevisiae. Mullen, J.R., Kaliraman, V., Ibrahim, S.S., Brill, S.J. Genetics (2001) [Pubmed]
  15. Interaction between yeast sgs1 helicase and DNA topoisomerase III. Bennett, R.J., Noirot-Gros, M.F., Wang, J.C. J. Biol. Chem. (2000) [Pubmed]
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