Human DICER helicase domain recruits PKR and modulates its antiviral activity.

Thomas C Montavon,Béatrice Chane-Woon-Ming,Mathieu Lefèvre,Morgane Baldaccini,Philippe Hammann,Sébastien Pfeffer,Johana Chicher,Erika Girardi,Mélanie Messmer,Stacy M Horner

doi:10.1371/journal.ppat.1009549

Abstract

The antiviral innate immune response mainly involves type I interferon (IFN) in mammalian cells. The contribution of the RNA silencing machinery remains to be established, but several recent studies indicate that the ribonuclease DICER can generate viral siRNAs in specific conditions. It has also been proposed that type I IFN and RNA silencing could be mutually exclusive antiviral responses. In order to decipher the implication of DICER during infection of human cells with alphaviruses such as the Sindbis virus and Semliki forest virus, we determined its interactome by proteomics analysis. We show that DICER specifically interacts with several double-stranded RNA binding proteins and RNA helicases during viral infection. In particular, proteins such as DHX9, ADAR-1 and the protein kinase RNA-activated (PKR) are enriched with DICER in virus-infected cells. We demonstrate that the helicase domain of DICER is essential for this interaction and that its deletion confers antiviral properties to this protein in an RNAi-independent, PKR-dependent, manner.

Highlights

In mammalian cells, the main antiviral defense system involves the activation of a signaling cascade relying on production of type I interferon (IFN I)
We determined its interactome in human cells and showed that RNA binding proteins such as protein kinase R (PKR) are enriched upon infection with the Sindbis virus or the Semliki forest virus
We determined that the N terminal helicase domain of the DICER protein acts as a platform to recruit these factors during infection and that its deletion confers an antiviral activity to DICER

Summary

Introduction

The main antiviral defense system involves the activation of a signaling cascade relying on production of type I interferon (IFN I) This pathway depends on the recognition of extrinsic signals or pathogen associated molecular patterns (PAMPs) by dedicated host receptors. RLRs comprise RIG-I, MDA5 and LGP2 and transduce viral infection signals to induce expression of IFN I cytokines that act in autocrine and paracrine fashions. These cytokines trigger the expression of hundreds of interferon-stimulated genes (ISGs) to stop the virus in its tracks [2]. PKR is involved in other cellular pathways including apoptosis, autophagy and cell cycle [3,8]

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