question: What is the mechanism of action of APOBEC3G cytidine deaminase to inhibit HIV-1 replication?
answer: During reverse transcription, APOBEC3G deaminates dC to dU in nascent minus-strand viral DNA, resulting in G-to-A hypermutation in the plus strand DNA to inhibit replication of HIV-1, due to viral cDNA degradation, production of non-functional proteins, formation of undesired stop codons and decreased viral protein synthesis. In an additional line of antiviral defense, APOBEC3G induces deamination of the apical loop cytidine of the trans-activation response (TAR) element, a short stem-loop RNA structure required for binding of elongation factors during HIV-1 transcription elongation, resulting in accumulation of short viral transcripts and production of lower amounts of full-length HIV-1 transcripts in Vif-deficient HIV-1-infected cells.