The Disassociation of A3G-Related HIV-1 cDNA G-to-A Hypermutation to Viral Infectivity

Abstract

APOBEC3G (A3G) restricts HIV-1 replication primarily by reducing viral cDNA and inducing G-to-A hypermutations in viral cDNA. HIV-1 encodes virion infectivity factor (Vif) to counteract A3G primarily by excluding A3G viral encapsidation. Even though the Vif-induced exclusion is robust, studies suggest that A3G is still detectable in the virion. The impact of encapsidated A3G in the HIV-1 replication is unclear. Using a highly sensitive next-generation sequencing (NGS)-based G-to-A hypermutation detecting assay, we found that wild-type HIV-1 produced from A3G-expressing T-cells induced higher G-to-A hypermutation frequency in viral cDNA than HIV-1 from non-A3G-expressing T-cells. Interestingly, although the virus produced from A3G-expressing T-cells induced higher hypermutation frequency, there was no significant difference in viral infectivity, revealing a disassociation of cDNA G-to-A hypermutation to viral infectivity. We also measured G-to-A hypermutation in the viral RNA genome. Surprisingly, our data showed that hypermutation frequency in the viral RNA genome was significantly lower than in the integrated DNA, suggesting a mechanism exists to preferentially select intact genomic RNA for viral packing. This study revealed a new insight into the mechanism of HIV-1 counteracting A3G antiviral function and might lay a foundation for new antiviral strategies.

Keywords

• APOBEC3G
• cytidine deaminase
• G-to-A hypermutation
• HIV-1 Vif
• proteasomal degradation
• encapsidation