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Topoisomerase (DNA) III alpha
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols TOP3A ; TOP3; ZGRF7
External IDs OMIM601243 MGI1197527 HomoloGene3394 GeneCards: TOP3A Gene
EC number
RNA expression pattern
PBB GE TOP3A 204946 s at tn.png
PBB GE TOP3A 214300 s at tn.png
More reference expression data
Species Human Mouse
Entrez 7156 21975
Ensembl ENSG00000177302 ENSMUSG00000002814
UniProt Q13472 O70157
RefSeq (mRNA) NM_004618 NM_009410
RefSeq (protein) NP_004609 NP_033436
Location (UCSC) Chr 17:
18.17 – 18.22 Mb
Chr 11:
60.74 – 60.78 Mb
PubMed search [1] [2]

DNA topoisomerase 3-alpha is an enzyme that in humans is encoded by the TOP3A gene.[1][2]

This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This enzyme catalyzes the transient breaking and rejoining of a single strand of DNA which allows the strands to pass through one another, thus reducing the number of supercoils and altering the topology of DNA. This enzyme forms a complex with BLM which functions in the regulation of recombination in somatic cells.[2]


TOP3A has been shown to interact with Bloom syndrome protein.[3][4][5][6]


  1. ^ Elsea SH, Fritz E, Schoener-Scott R, Meyn MS, Patel PI (February 1998). "Gene for topoisomerase III maps within the Smith-Magenis syndrome critical region: analysis of cell-cycle distribution and radiation sensitivity". Am J Med Genet 75 (1): 104–8. doi:10.1002/(SICI)1096-8628(19980106)75:1<104::AID-AJMG21>3.0.CO;2-P. PMID 9450867. 
  2. ^ a b "Entrez Gene: TOP3A topoisomerase (DNA) III alpha". 
  3. ^ Wu, L; Davies S L; North P S; Goulaouic H; Riou J F; Turley H; Gatter K C; Hickson I D (March 2000). "The Bloom's syndrome gene product interacts with topoisomerase III". J. Biol. Chem. (UNITED STATES) 275 (13): 9636–44. doi:10.1074/jbc.275.13.9636. ISSN 0021-9258. PMID 10734115. 
  4. ^ Freire, R; d'Adda Di Fagagna F, Wu L, Pedrazzi G, Stagljar I, Hickson I D, Jackson S P (August 2001). "Cleavage of the Bloom's syndrome gene product during apoptosis by caspase-3 results in an impaired interaction with topoisomerase IIIα". Nucleic Acids Res. (England) 29 (15): 3172–80. doi:10.1093/nar/29.15.3172. PMC 55826. PMID 11470874. 
  5. ^ Hu, P; Beresten S F; van Brabant A J; Ye T Z; Pandolfi P P; Johnson F B; Guarente L; Ellis N A (June 2001). "Evidence for BLM and Topoisomerase IIIalpha interaction in genomic stability". Hum. Mol. Genet. (England) 10 (12): 1287–98. doi:10.1093/hmg/10.12.1287. ISSN 0964-6906. PMID 11406610. 
  6. ^ Brosh, R M; Li J L; Kenny M K; Karow J K; Cooper M P; Kureekattil R P; Hickson I D; Bohr V A (August 2000). "Replication protein A physically interacts with the Bloom's syndrome protein and stimulates its helicase activity". J. Biol. Chem. (UNITED STATES) 275 (31): 23500–8. doi:10.1074/jbc.M001557200. ISSN 0021-9258. PMID 10825162. 

Further reading[edit]