The mutational specificity of the Dbh lesion bypass polymerase and its implications

J Biol Chem. 2002 Aug 2;277(31):28157-66. doi: 10.1074/jbc.M202607200. Epub 2002 May 21.


The Dbh polymerase of Sulfolobus solfataricus is a member of the recently described family of low fidelity DNA polymerases involved in bypass of DNA lesions. To investigate the enzymatic properties of Dbh, we characterized the errors made by this polymerase in vitro. Not only is Dbh much less accurate than the "classical" polymerases, but it showed a remarkable tendency to skip over a template pyrimidine positioned immediately 3' to a G residue, generating a single-base deletion. Single-turnover kinetic measurements suggest possible mechanisms. First, Dbh shows a bias in favor of dCTP, such that the rate of incorporation of dCTP opposite a template G is about 10-fold faster than for the other three dNTPs opposite their complementary partners. On a DNA substrate corresponding to a frameshift hotspot, the rate of frameshift insertion of dCTP opposite a template G that is one residue 5' to the expected templating position is approximately equal to the rate of the non-frameshifted C-dGTP insertion. We suspect that the unusual mutational specificity of Dbh (which is shared with other polymerases from the DinB branch of the bypass polymerase family) may be related to the type of DNA lesion(s) that it serves to bypass in vivo.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Archaeal Proteins*
  • Base Sequence
  • DNA-Directed DNA Polymerase / metabolism*
  • Deoxyribonucleotides / metabolism
  • Frameshift Mutation*
  • Kinetics
  • Molecular Sequence Data
  • Mutation*
  • Mutation, Missense
  • Oligodeoxyribonucleotides / biosynthesis
  • Oligodeoxyribonucleotides / chemistry
  • Reproducibility of Results
  • Substrate Specificity
  • Sulfolobus / enzymology*
  • Thermodynamics


  • Archaeal Proteins
  • Deoxyribonucleotides
  • Oligodeoxyribonucleotides
  • Dbh protein, Sulfolobus solfataricus
  • DNA-Directed DNA Polymerase