Human apolipoprotein B mRNA editing enzyme catalytic polypeptide-like 3 (APOBEC3; A3) proteins, particularly APOBEC3G (A3G), are cellular DNA cytosine deaminases and one of the well-studied restriction factors that inhibit the replication of human immunodeficiency virus type 1 (HIV-1), the causative agent of acquired immunodeficiency syndrome (AIDS) in humans4. Here, APOBEC3G is linked to AIDS.