ASK1 restores the antiviral activity of APOBEC3G by disrupting HIV-1 Vif-mediated counteraction.

Kei Miyakawa,Satoko Matsunaga,Keisuke Shindo,Hidenori Ichijo,Ayumi Kudoh,Hironori Sato,Ryo Morishita,Masaru Yokoyama,Kazuhiko Kanou,Atsushi Matsuzawa,Naoki Yamamoto,Tomohiko Tamura,Hirokazu Kimura,Akifumi Takaori-Kondo,Akihide Ryo

doi:10.1038/ncomms7945

Abstract

APOBEC3G (A3G) is an innate antiviral restriction factor that strongly inhibits the replication of human immunodeficiency virus type 1 (HIV-1). An HIV-1 accessory protein, Vif, hijacks the host ubiquitin–proteasome system to execute A3G degradation. Identification of the host pathways that obstruct the action of Vif could provide a new strategy for blocking viral replication. We demonstrate here that the host protein ASK1 (apoptosis signal-regulating kinase 1) interferes with the counteraction by Vif and revitalizes A3G-mediated viral restriction. ASK1 binds the BC-box of Vif, thereby disrupting the assembly of the Vif–ubiquitin ligase complex. Consequently, ASK1 stabilizes A3G and promotes its incorporation into viral particles, ultimately reducing viral infectivity. Furthermore, treatment with the antiretroviral drug AZT (zidovudine) induces ASK1 expression and restores the antiviral activity of A3G in HIV-1-infected cells. This study thus demonstrates a distinct function of ASK1 in restoring the host antiviral system that can be enhanced by AZT treatment.

Highlights

APOBEC3G (A3G) is an innate antiviral restriction factor that strongly inhibits the replication of human immunodeficiency virus type 1 (HIV-1)
HEK293 cells were cotransfected with plasmids encoding Vif, green fluorescent protein (GFP)-A3G, and the indicated MAP3Ks, and GFP intensities were assessed with flow cytometry and immunoblot analysis
The activation or suppression of ERK, p38- and JNK-mediated MAPK pathways did not alter the ability of apoptosis signal-regulating kinase 1 (ASK1) to bind and counteract Vif (Supplementary Fig. 1a–c)

Summary

Introduction

APOBEC3G (A3G) is an innate antiviral restriction factor that strongly inhibits the replication of human immunodeficiency virus type 1 (HIV-1). One such factor is an editing enzyme for nucleic acids, APOBEC3G (apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like 3G, hereafter referred to as A3G) This protein severely restricts the replication of numerous viruses, including human immunodeficiency virus type 1 (HIV-1)[4] and hepatitis B virus[5], by extensively deaminating cytosine residues in the viral genome during reverse transcription. The strategies to promote A3G stability and its incorporation into virions could be a new avenue for the development of new antiviral drugs In this regard, the disruption of any of the steps required for the effect of Vif on A3G would be expected to restore cellular A3G levels and virus restriction. The identification of host regulators of Vif may provide an alternative therapeutic strategy for HIV-1 infection that preserves the antiviral activity of the host defense system

Methods

Results

Conclusion