Kinetics of deoxyribonucleotide insertion and extension at abasic template lesions in different sequence contexts using HIV-1 reverse transcriptase

J Biol Chem. 1993 Nov 5;268(31):23567-72.


Deoxyribonucleotide insertion efficiencies were measured opposite site-directed abasic template lesions using human immunodeficiency virus 1 reverse transcriptase (HIV-1RT), and the efficiencies to continue primer synthesis beyond the lesion, by addition of the "next correct" deoxynucleotide, were measured as a function of sequence context. Insertion of purines was favored over pyrimidines, A > G > T approximately C. Primer extension past the lesion occurred by two distinct mechanisms, either by direct or by misalignment extension. An "A-rule" appeared to hold for the case of direct extension, where the abasic template moiety is intrahelical, aligned opposite the primer 3'-terminus. In misalignment extension, the primer terminus is realigned from a site directly opposite the lesion to a new position opposite a neighboring template base 5' to the lesion. Direct extension efficiencies were measured in 16 different configurations, by varying 4 bases at the primer 3'-termini and 4 at the 5'-side (downstream) of the lesion. The predominant order of direct extension was A > G > T approximately C, similar to that observed for insertion. Reduced primer extension rates were not caused by a reduction in HIV-1 RT-DNA binding. Primers terminating in C showed inefficient direct extension, but were readily extended via misaligned configurations. The ratios of direct-to-misalignment extension efficiencies were 27:1, 2.5:1, and 1:25 for A, G, and C opposite the lesion, respectively. For the case of primers terminating in T, misalignment extension was not observed. A striking result was that while primers were extended past an abasic lesion by HIV-1 RT in both direct and misalignment modes, avian myeloblastosis virus RT failed to catalyze significant extension by either mode.

Publication types

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

MeSH terms

  • Animals
  • Avian Myeloblastosis Virus / enzymology
  • DNA Damage
  • DNA Polymerase II / metabolism
  • DNA Repair
  • Drosophila melanogaster / enzymology
  • HIV Reverse Transcriptase
  • Kinetics
  • RNA-Directed DNA Polymerase / metabolism*
  • Substrate Specificity
  • Templates, Genetic


  • HIV Reverse Transcriptase
  • RNA-Directed DNA Polymerase
  • DNA Polymerase II