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.
Design and 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.
Conclusion: 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.
aDepartment of Medicine, Division of Infectious Diseases, University of Pittsburgh School of Medicine, USA
bDepartment of Infectious Disease and Microbiology, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania, USA
cMolecular Interactions Group, Centre for Virology, Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Australia
dSchool of Applied Sciences and Engineering, Monash University, Churchill, Australia
eDepartment of Microbiology, Monash University, Clayton, Australia
fDepartment of Medicine, Monash University, Melbourne, Victoria, Australia.
Received 23 July, 2009
Revised 19 November, 2009
Accepted 10 December, 2009
Correspondence to Nicolas Sluis-Cremer, Department of Medicine, Division of Infectious Diseases, University of Pittsburgh School of Medicine, 817 Scaife Hall, 3550 Terrace Street, Pittsburgh, PA 15261, USA. Tel: +1 412 648 8457; fax: +1 412 648 8521; e-mail: email@example.com