Background:The cellular DNA repair machinery completes the 5Ј-end gap repair of HIV-1 integration. Results: The 5Ј-end DNA gap repair of HIV-1 integration depends on dNTP availability in macrophages, monocytes, and CD4

Human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT) has a unique tight binding to dNTP substrates. Structural modeling of Ala-114 of HIV-1 RT suggests that longer side chains at this residue can reduce the space normally occupied by the sugar moiety of an incoming dNTP. Indeed, mutations at Ala-114 decrease the ability of RT to synthesize DNA at low dNTP concentrations and reduce the dNTP-binding affinity (Kd) of RT. However, the Kd values of WT and A114C RT remained equivalent with an acylic dNTP substrate. Finally, mutant A114 RT HIV-1 vectors displayed a greatly reduced transduction in nondividing human lung fibroblasts (HLFs), while WT HIV-1 vector efficiently transduced both dividing and nondividing HLFs. Together these data support that the A114 residue of HIV-1 RT plays a key mechanistic role in the dNTP binding of HIV-1 RT and the unique viral infectivity of target cell types with low dNTP pools.

We recently reported that the M184I 3TC resistant mutation reduces RT binding affinity to dNTP substrates. First, the HIV-1 M184I mutant vector displays reduced transduction efficiency compared to wild type (WT) RT vector, which could be rescued by both elevating the cellular dNTP concentration and incorporating WT RT molecules into the M184I vector particles. Second, the central polypurine tract (cPPT) mutation and M184I mutation additively reduced the vector transduction to almost undetectable levels, particularly in nondividing cells. Third, the M184I (−) cPPT vector became significantly more sensitive to 3TC than the M184I (+) cPPT vector, but not to AZT or Nevirapine in the dividing cells. Finally, this 3TC sensitizing effect of the cPPT inactivation of the M184I vector was reversed by elevating dCTP level, but not by other three dNTPs. These data support a mechanistic interaction between cPPT and M184I RT with respect to viral replication and sensitivity to 3TC.