A human 5'-tyrosyl DNA phosphodiesterase that repairs topoisomerase-mediated DNA damage

Nature. 2009 Oct 1;461(7264):674-8. doi: 10.1038/nature08444.


Topoisomerases regulate DNA topology and are fundamental to many aspects of chromosome metabolism. Their activity involves the transient cleavage of DNA, which, if it occurs near sites of endogenous DNA damage or in the presence of topoisomerase poisons, can result in abortive topoisomerase-induced DNA strand breaks. These breaks feature covalent linkage of the enzyme to the DNA termini by a 3'- or 5'-phosphotyrosyl bond and are implicated in hereditary human disease, chromosomal instability and cancer, and underlie the clinical efficacy of an important class of anti-tumour poisons. The importance of liberating DNA termini from trapped topoisomerase is illustrated by the progressive neurodegenerative disease observed in individuals containing a mutation in tyrosyl-DNA phosphodiesterase 1 (TDP1), an enzyme that cleaves 3'-phosphotyrosyl bonds. However, a complementary human enzyme that cleaves 5'-phosphotyrosyl bonds has not been reported, despite the effect of DNA double-strand breaks containing such termini on chromosome instability and cancer. Here we identify such an enzyme in human cells and show that this activity efficiently restores 5'-phosphate termini at DNA double-strand breaks in preparation for DNA ligation. This enzyme, TTRAP, is a member of the Mg(2+)/Mn(2+)-dependent family of phosphodiesterases. Cellular depletion of TTRAP results in increased susceptibility and sensitivity to topoisomerase-II-induced DNA double-strand breaks. TTRAP is, to our knowledge, the first human 5'-tyrosyl DNA phosphodiesterase to be identified, and we suggest that this enzyme is denoted tyrosyl DNA phosphodiesterase-2 (TDP2).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Camptothecin / pharmacology
  • Cell Extracts / chemistry
  • Cell Line, Tumor
  • DNA Breaks, Double-Stranded
  • DNA Breaks, Single-Stranded
  • DNA Damage* / drug effects
  • DNA Repair*
  • DNA Topoisomerases / metabolism*
  • DNA Topoisomerases, Type I / metabolism
  • DNA Topoisomerases, Type II / metabolism
  • DNA-Binding Proteins
  • Etoposide / pharmacology
  • Female
  • Gene Library
  • Genetic Complementation Test
  • Humans
  • Male
  • Mice
  • Nuclear Proteins / deficiency
  • Nuclear Proteins / genetics
  • Nuclear Proteins / isolation & purification
  • Nuclear Proteins / metabolism*
  • Phosphoric Diester Hydrolases / genetics
  • Phosphoric Diester Hydrolases / metabolism
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Suppression, Genetic
  • Transcription Factors / deficiency
  • Transcription Factors / genetics
  • Transcription Factors / isolation & purification
  • Transcription Factors / metabolism*


  • Cell Extracts
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Transcription Factors
  • Etoposide
  • Phosphoric Diester Hydrolases
  • TDP1 protein, human
  • TDP2 protein, human
  • DNA Topoisomerases
  • DNA Topoisomerases, Type I
  • DNA Topoisomerases, Type II
  • Camptothecin