title: Thymidine analogue excision and discrimination modulated by mutational complexes including single amino acid deletions of Asp-67 or Thr-69 in HIV-1 reverse transcriptase.
abstract: Single amino acid deletions in the β3-β4 hairpin loop of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) have been identified in heavily treated patients. The deletion of Asp-67 together with mutations T69G and K70R (Δ67 complex) are usually associated with thymidine analog resistance mutations (TAMs) (e.g. M41L, T215Y, etc.) while the deletion of Thr-69 (Δ69) is rarely found in isolates containing TAMs. Here, we show that the complex Δ67/T69G/K70R enhances ATP-dependent phosphorolytic activity on primers terminated with 3'-azido-3'-deoxythymidine (AZT) or 2',3'-didehydro-2',3'-dideoxythymidine (d4T) both in the presence or absence of TAMs (i.e. M41L/T215Y), while Δ69 (or the complex S68G/Δ69/K70G) antagonize the effects of TAMs in ATP-mediated excision. These effects are consistent with AZT susceptibility data obtained with recombinant HIV-1 bearing the relevant RTs. Molecular dynamics studies based on models of wild-type HIV-1 RT and mutant Δ69, Δ67/T69G/K70R, and D67N/K70R RTs support a relevant role for Lys/Arg-70 in the excision reaction. In Δ69 RT, the side chain of Lys-70 locates away from the putative pyrophosphate binding site. Therefore, its participation in interactions required for the excision reaction is unlikely. Our theoretical studies also suggest a role for Lys-219 in thymidine analog excision/discrimination. However, pre-steady-state kinetics revealed only minor differences in selectivity of AZT-triphosphate versus dTTP between deletion-containing RTs and their homologous enzymes having the K219E mutation. K219E reduced both ATP- and pyrophosphate-mediated excision of primers terminated with thymidine analogues, only when introduced in RTs bearing Δ69 or S68G/Δ69/K70G, providing further biochemical evidence that explains the lack of association of Δ69 and TAMs in HIV-1 isolates.
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, 28049 Madrid, Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: Kisic
authors.forename: Tania
authors.initials: T
authors.lastname: Matamoros
authors.forename: María
authors.initials: M
authors.lastname: Nevot
authors.forename: Jesús
authors.initials: J
authors.lastname: Mendieta
authors.forename: Javier
authors.initials: J
authors.lastname: Martinez-Picado
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Martínez
authors.forename: Luis
authors.initials: L
authors.lastname: Menéndez-Arias
mesh_terms: D004279:DNA, Viral / Q000096:biosynthesis; D054303:HIV Reverse Transcriptase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015497:HIV-1 / Q000201:enzymology / Q000235:genetics; D006801:Humans; D007700:Kinetics; D009154:Mutation; D018119:Stavudine / Q000737:chemistry / Q000378:metabolism; D015215:Zidovudine / Q000737:chemistry / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D015215:Zidovudine; D018119:Stavudine; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase