Apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G) is a host cellular protein with a broad antiviral activity.
It inhibits infectivitiy of a wide variety of retroviruses by deaminating deoxycytidine (dC) into deoxyuridine (dU) in newly synthesized minus strand DNA, resulting in G-to-A hypermutation of the viral plus strand DNA.
APOBEC3G, also known as CEM15 [1], is a host cellular protein which has a broad antiviral activity on a wide variety of retroviruses including HIV-1, other lentiviruses, and murine leukemia virus (MLV) [2-4].
The protein belongs to the Apobec superfamily of cytidine deaminases [5] and inhibits the infectivity of these viruses by being packaged into virions.
During reverse transcription, it deaminates deoxycytidine (dC) into deoxyuridine (dU) in newly synthesized minus strand DNA, resulting in either G-to-A hypermutation of the viral plus strand DNA or degradation of dU-rich reverse transcripts [3,6-8], though several resent studies suggest cytidine deaminase adtivity is essential but not a sole determinant for antiviral activity of APOBEC3G.
[7].
Most lentiviruses express an accessory protein called virion infectivity factor (Vif) which blocks the antiviral function of APOBEC3G by preventing its packaging into virions.
Vif binds to APOBEC3G and induces its ubiquitination and subsequent degradation by the proteasome [9-13].
It has also been reported that APOBEC3G inhibits the replication of hepatitis B virus (HBV) without inducing G-to-A hypermutation [14].
This suggests that APOBEC3G has a broad antiviral activity not only on retroviruses but also on other viruses through different mechanisms from that on retroviruses.
