Functional role of HIV-1 virion-associated uracil DNA glycosylase 2 in the correction of G:U mispairs to G:C pairs.

Human monocytes/macrophages are target cells for HIV-1 infection. As other non-dividing cells, they are characterized by low and imbalanced intracellular dNTP pool levels and an excess of dUTP. The replication of HIV-1 in this cellular context favors misincorporation of uracil residues into viral DNA because of the use of dUTP in place of dCTP. We have previously reported that the host uracil DNA glycosylase enzyme UNG2 is packaged into HIV-1 viral particles via a specific association with the integrase domain of the Gag-Pol precursor. In this study, we investigated whether virion-associated UNG2 plays a role similar to that of its cellular counterpart. We show that the L172A mutation of integrase impaired the packaging of UNG2 into viral particles. Using a primer-template DNA substrate containing G:U mispairs, we demonstrate that wild-type viral lysate has the ability to repair G:U mismatched pairs to G:C matched pairs, in contrast to UNG2-deficient viral lysate. Moreover, no correction of G:T mispairs by wild-type HIV-1 viral lysate was observed, which argues for the specificity of the repair process. We also show that UNG2 physically associates with the viral reverse transcriptase enzyme. Altogether our data indicate for the first time that a uracil repair pathway is specifically associated with HIV-1 viral particles. However, the molecular mechanism of this process remains to be characterized further.