APOBEC3-mediated restriction of RNA virus replication

Aleksandra Milewska,Philip Vkovski,Volker Thiel,Eveline Kindler,Slawomir Zeglen,Marek Ochman,Krzysztof Pyrc,Slawomir Zeglen,Zenon Rajfur

doi:10.1038/s41598-018-24448-2

Aleksandra Milewska, Philip Vkovski + Show 7 more

Open Access

https://doi.org/10.1038/s41598-018-24448-2

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Abstract

APOBEC3 family members are cytidine deaminases with roles in intrinsic responses to infection by retroviruses and retrotransposons, and in the control of other DNA viruses, such as herpesviruses, parvoviruses and hepatitis B virus. Although effects of APOBEC3 members on viral DNA have been demonstrated, it is not known whether they edit RNA genomes through cytidine deamination. Here, we investigated APOBEC3-mediated restriction of Coronaviridae. In experiments in vitro, three human APOBEC3 proteins (A3C, A3F and A3H) inhibited HCoV-NL63 infection and limited production of progeny virus, but did not cause hypermutation of the coronaviral genome. APOBEC3-mediated restriction was partially dependent on enzyme activity, and was reduced by the use of enzymatically inactive APOBEC3. Moreover, APOBEC3 proteins bound to the coronaviral nucleoprotein, and this interaction also affected viral replication. Although the precise molecular mechanism of deaminase-dependent inhibition of coronavirus replication remains elusive, our results further our understanding of APOBEC-mediated restriction of RNA virus infections.

Highlights

Apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like type 3 (APOBEC3) proteins are Zn2+ dependent cytidine deaminases that belong to the APOBEC superfamily
Modulation of human APOBEC3-family transcript levels in human airway epithelium (HAE) cultures during coronavirus infection was evaluated by quantitative reverse transcription (RT)-PCR with primers and standards developed in our lab
The same six genes (APOBEC3A, APOBEC3C, APOBEC3D, APOBEC3F, APOBEC3G and APOBEC3H) were expressed during human coronaviruses (HCoVs)-NL63 infection, and these genes were analysed in subsequent experiments

Summary

Introduction

Apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like type 3 (APOBEC3) proteins are Zn2+ dependent cytidine deaminases that belong to the APOBEC superfamily. The mechanisms and selective pressures that led to the APOBEC3 gene expansion in humans are unclear, but it is believed that all the genes originated from duplication of a single-copy primordial APOBEC3 gene This multiplication may have provided protection from genomic instability caused by human endogenous retroviruses and retrotransposons[2]. Mutational frequencies can exceed 10% of all G residues (hypermutation), and may result in inhibition of viral replication This activity is blocked by Vif protein, which binds to and ubiquitinates A3G, directing it for degradation in the Astronomy and Applied Computer Sciences, Jagiellonian University, Lojasiewicza 11, 30-348, Krakow, Poland. Six human coronaviruses (HCoVs) have been identified, four of which (HCoV-OC43, HCoV229E, HCoV-NL63 and HCoV-HKU1) circulate continuously in human populations These four viruses cause the common cold in otherwise healthy adults, and may cause more severe symptoms in young, elderly and immunocompromised individuals[19,20,21,22]. MERS-CoV was isolated in 2012 and is associated with severe pneumonia and renal failure, with a mortality rate of ~30%25,26

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