Promyelocytic Leukemia Restricts Enterovirus 71 Replication by Inhibiting Autophagy

Deyan Chen,Chunhong Feng,Zhiwei Wu,Nan Zheng,Xiaoyan Tian

doi:10.3389/fimmu.2018.01268

Deyan Chen, Chunhong Feng + Show 3 more

Open Access

https://doi.org/10.3389/fimmu.2018.01268

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Abstract

The promyelocytic leukemia (PML) protein, also known as TRIM19, functions as a major organizer of PML nuclear bodies (NBs) in most mammalian cells and plays important roles in antiviral activities against both DNA and RNA viruses. In this study, we found that the downregulation of PML rendered HeLa cells more susceptible to infection by enterovirus 71 (EV71), and the overexpression of the PMLIII or PMLIV isoforms inhibited viral protein expression and resulted in viral titers that were 2–3 log units lower than those in the control. Using short interfering RNAs, the downregulation of either the PMLIII or PMLIV isoform increased both viral protein VP1 expression and viral production. The PML repression of EV71 replication was partially mediated by the inhibition of autophagy, and PML deficiency triggered autophagy. Furthermore, the EV71 infection resulted in a reduction in PML independent of the proteasome pathway. Instead, PML degradation was mediated by virus protease 3Cpro. In conclusion, PML contributes to a cellular antiviral effect by inhibiting autophagy, which is countered by a disruption of promyelocytic leukemia protein-nuclear bodies mediated by viral protease 3Cpro.

Highlights

Promyelocytic leukemia protein-nuclear bodies (PML-NBs) are dynamic cellular structures consisting of numerous transiently and permanently localized proteins
To investigate the roles of PML in the replication of enterovirus 71 (EV71), we determined the effects of the down-modulation of endogenous PML on EV71 replication
The effect of PML on EV71 replication and viral production was assessed by performing a TCID50 assay and Western blot analysis for viral protein VP1, respectively

Summary

Introduction

Promyelocytic leukemia protein-nuclear bodies (PML-NBs) are dynamic cellular structures consisting of numerous transiently and permanently localized proteins. Promyelocytic leukemia (PML), known as TRIM19, MYL, PP8675, or RNF71, is the major component of PML-NBs and plays important roles in genome stability, programmed cell death, and antiviral activities [1]. All isoforms share a similar N-terminal region encoded by exons 1–3 and containing the RBCC motif through which PML multimerizes to form a ring-like structure that binds to the nuclear matrix, forming PML-NBs [1]. The PML promoter region contains targets for STATs, IRFs, and p53, and the PML gene is directly inducible by interferons (IFNs) including type I and type II, leading to an increased expression of PML isoforms, increased numbers, and bigger size of PML-NBs [2]. PML SUMOylation was needed to recruit other PML-NB components and to maintain the biogenesis of PML nuclear bodies (NBs) [3, 8]

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