Mouse APOBEC3 interferes with autocatalytic cleavage of murine leukemia virus Pr180gag-pol precursor and inhibits Pr65gag processing

Yoshiyuki Hakata,Masaaki Miyazawa,Jun Li,Rie Shimizu,Yuki Tanaka,Takahiro Fujino,Susan R Ross

doi:10.1371/journal.ppat.1008173

Yoshiyuki Hakata, Masaaki Miyazawa + Show 5 more

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https://doi.org/10.1371/journal.ppat.1008173

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Abstract

Mouse APOBEC3 (mA3) inhibits murine leukemia virus (MuLV) replication by a deamination-independent mechanism in which the reverse transcription is considered the main target process. However, other steps in virus replication that can be targeted by mA3 have not been examined. We have investigated the possible effect of mA3 on MuLV protease-mediated processes and found that mA3 binds both mature viral protease and Pr180gag-pol precursor polyprotein. Using replication-competent MuLVs, we also show that mA3 inhibits the processing of Pr65 Gag precursor. Furthermore, we demonstrate that the autoprocessing of Pr180gag-pol is impeded by mA3, resulting in reduced production of mature viral protease. This reduction appears to link with the above inefficient Pr65gag processing in the presence of mA3. Two major isoforms of mA3, exon 5-containing and -lacking ones, equally exhibit this antiviral activity. Importantly, physiologically expressed levels of mA3 impedes both Pr180gag-pol autocatalysis and Pr65gag processing. This blockade is independent of the deaminase activity and requires the C-terminal region of mA3. These results suggest that the above impairment of Pr180gag-pol autoprocessing may significantly contribute to the deaminase-independent antiretroviral activity exerted by mA3.

Highlights

Apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3 (APOBEC3) belongs to the APOBEC family of cellular proteins, which includes activation-induced cytidine deaminase (AID), APOBEC1, APOBEC2 and APOBEC4
Soon after the identification of the polynucleotide cytidine deaminase APOBEC3 as a host restriction factor against vif-deficient HIV, it was noticed that deamination-independent mechanisms are involved in the inhibition of viral replication in addition to the deaminase-dependent mechanism
We previously showed that mouse APOBEC3 physiologically restricted mouse retrovirus replication in their natural hosts without causing significant G-to-A hypermutations

Summary

Introduction

Apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3 (APOBEC3) belongs to the APOBEC family of cellular proteins, which includes activation-induced cytidine deaminase (AID), APOBEC1, APOBEC2 and APOBEC4. In the infected host cells, APOBEC3G deaminates cytosines to uracils in the nascent minus-strand viral cDNA during reverse transcription, resulting in the production of the plus strand with high levels of G-to-A mutations [14]. These mutations may generate undesired stop codons and resultantly disturb the production of functional viral proteins. A current model for the deamination-independent antiviral activity employs oligomerization of APOBEC3 on viral genomic RNA and minus-strand DNA, which may sterically block the elongation and accumulation of the products of reverse transcription [26]. It remains unknown whether deamination-independent antiviral action of APOBEC3 is solely attributed to reverse transcription as the target process

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