Nucleotide Sugar Pucker Preference Mitigates Excision by HIV-1 RT.

A series of DNA primers containing nucleotides with various sugar pucker conformations at the 3'-terminus were chemically synthesized by solid-phase synthesis. The ability of wild-type (WT) HIV-1 reverse transcriptase (RT) and AZT-resistant (AZTr) RT to excise the 3'-terminal nucleotide was assessed. Nucleosides with a preference for the North conformation were more refractory to excision by both WT-RT and AZTr-RT. We found that DNA primers that contain North puckered-nucleotides at the 3'-terminus can also affect the translocation status of the RT/template/primer complex, which provides an underlying mechanism to avoid being excised. Together, these results point to a correlation between the sugar conformation of the 3'-terminal nucleotide, the precise position of HIV-1 RT on its nucleic acid substrate, and, in turn, its catalytic function. Nucleotide sugar conformation is therefore an important parameter in defining the susceptibility to RT-catalyzed phosphorolytic excision.