title: N348I in reverse transcriptase provides a genetic pathway for HIV-1 to select thymidine analogue mutations and mutations antagonistic to thymidine analogue mutations.
abstract: OBJECTIVE
  Several nonnucleoside (e.g. Y181C) and nucleoside (e.g. L74V and M184V) resistance mutations in HIV-1 reverse transcriptase are antagonistic toward thymidine analogue mutations (TAMs) that confer zidovudine (ZDV) resistance. The N348I mutation in the connection domain of reverse transcriptase also confers ZDV resistance; however, the mechanisms involved are different from TAMs. In this study, we examined whether N348I compensates for the antagonism of the TAM K70R by Y181C, L74V and M184V.
  
  
  METHODS
  The ZDV monophosphate and ribonuclease H activities of recombinant-purified HIV-1 reverse transcriptase-containing combinations of K70R, N348I and Y181C, L74V or M184V were assessed using standard biochemical and antiviral assays.
  
  
  RESULTS
  As expected, the introduction of the Y181C, L74V or M184V mutations into K70R HIV-1 reverse transcriptase significantly diminished the ATP-mediated ZDV monophosphate excision activity of the enzyme. However, the N348I mutation compensated for this antagonism on RNA/DNA template/primers by significantly decreasing the frequency of secondary ribonuclease H cleavages that reduce the overall efficiency of the excision reaction.
  
  
  CONCLUSIONS
  The acquisition of N348I in HIV-1 reverse transcriptase - which can occur early in therapy, oftentimes before TAMs - may provide a simple genetic pathway that allows the virus to select both TAMs and mutations that are antagonistic toward TAMs.
authors.affiliation: Department of Medicine, University of Pittsburgh School of Medicine, PA, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Radzio
authors.forename: Soo-Huey
authors.initials: SH
authors.lastname: Yap
authors.forename: Gilda
authors.initials: G
authors.lastname: Tachedjian
authors.forename: Nicolas
authors.initials: N
authors.lastname: Sluis-Cremer
mesh_terms: D024921:Drug Resistance, Multiple, Viral / Q000235:genetics*; D015658:HIV Infections / Q000188:drug therapy / Q000235:genetics; D054303:HIV Reverse Transcriptase / Q000235:genetics*; D015497:HIV-1 / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D006801:Humans; D009154:Mutation; D010641:Phenotype; D018894:Reverse Transcriptase Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D013936:Thymidine / Q000235:genetics; D019562:Viral Load; D015215:Zidovudine / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D018894:Reverse Transcriptase Inhibitors; D015215:Zidovudine; D054303:HIV Reverse Transcriptase; D013936:Thymidine