A point mutation in the human cytomegalovirus DNA polymerase gene confers resistance to ganciclovir and phosphonylmethoxyalkyl derivatives

Antimicrob Agents Chemother. 1993 Jan;37(1):19-25. doi: 10.1128/AAC.37.1.19.


Ganciclovir-resistant mutant 759rD100 derived from human cytomegalovirus strain AD169 contains two resistance mutations, one of which is in the UL97 gene and results in decreased ganciclovir phosphorylation in infected cells [V. Sullivan, C. L. Talarico, S. C. Stanat, M. Davis, D. M. Coen, and K. K. Biron, Nature (London) 358:162-164, 1992]. In the present study, we mapped the second mutation to a 4.1-kb DNA fragment containing the DNA polymerase gene and showed that it confers ganciclovir resistance without impairing phosphorylation. Sequence analysis of the 4.1-kb region revealed a single nucleotide change that resulted in a glycine-to-alanine substitution at position 987 within conserved region V of the DNA polymerase. Recombinant viruses constructed to contain the DNA polymerase mutation but not the phosphorylation defect displayed intermediate resistance (4- to 6-fold) to ganciclovir relative to the original mutant 759rD100 (22-fold); the recombinant viruses also displayed resistance to ganciclovir cyclic phosphate (7-fold), 1-(dihydroxy-2-propoxymethyl)-cytosine (12-fold), and the phosphonylmethoxyalkyl derivatives (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)adenine and (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (8- to 10-fold). However, the recombinant viruses remained susceptible to certain related compounds. These results imply that the human cytomegalovirus DNA polymerase is a selective target for the antiviral activities of ganciclovir, certain of its derivatives and phosphonomethoxyalkyl derivatives; support a role for region V in substrate recognition; and suggest the possibility of clinical resistance of human cytomegalovirus to these compounds because of polymerase mutations.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cytomegalovirus / drug effects
  • Cytomegalovirus / enzymology
  • Cytomegalovirus / genetics*
  • DNA-Directed DNA Polymerase / biosynthesis*
  • DNA-Directed DNA Polymerase / genetics
  • Drug Resistance, Microbial / genetics*
  • Ganciclovir / analogs & derivatives*
  • Ganciclovir / pharmacology*
  • Genes, Viral
  • Genetic Markers
  • Humans
  • Molecular Sequence Data
  • Organophosphorus Compounds / pharmacology*
  • Plasmids
  • Point Mutation*
  • Recombination, Genetic
  • Viral Plaque Assay


  • Genetic Markers
  • Organophosphorus Compounds
  • DNA-Directed DNA Polymerase
  • Ganciclovir