High-efficiency bypass of DNA damage by human DNA polymerase Q

EMBO J. 2004 Nov 10;23(22):4484-94. doi: 10.1038/sj.emboj.7600424. Epub 2004 Oct 21.


Endogenous DNA damage arises frequently, particularly apurinic (AP) sites. These must be dealt with by cells in order to avoid genotoxic effects. DNA polymerase theta; is a newly identified enzyme encoded by the human POLQ gene. We find that POLQ has an exceptional ability to bypass an AP site, inserting A with 22% of the efficiency of a normal template, and continuing extension as avidly as with a normally paired base. POLQ preferentially incorporates A opposite an AP site and strongly disfavors C. On nondamaged templates, POLQ makes frequent errors, incorporating G or T opposite T about 1% of the time. This very low fidelity distinguishes POLQ from other A-family polymerases. POLQ has three sequence insertions between conserved motifs in its catalytic site. One insert of approximately 22 residues into the tip of the polymerase thumb subdomain is predicted to confer considerable flexibility and additional DNA contacts to affect enzyme fidelity. POLQ is the only known enzyme that efficiently carries out both the insertion and extension steps for bypass of AP sites, commonly formed as endogenous genomic lesions.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Motifs
  • Amino Acid Sequence
  • Conserved Sequence
  • DNA Damage*
  • DNA-Directed DNA Polymerase / chemistry*
  • DNA-Directed DNA Polymerase / genetics
  • DNA-Directed DNA Polymerase / isolation & purification
  • DNA-Directed DNA Polymerase / metabolism
  • Humans
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Structure, Tertiary
  • Pyrimidine Dimers / chemistry
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Templates, Genetic
  • Thymine / analogs & derivatives*
  • Thymine / chemistry


  • Pyrimidine Dimers
  • Recombinant Proteins
  • thymine glycol
  • DNA polymerase theta
  • DNA-Directed DNA Polymerase
  • Thymine