Article

Viral apoptosis is induced by IRF-3-mediated activation of Bax.

Department of Molecular Genetics, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
The EMBO Journal (Impact Factor: 10.75). 04/2010; 29(10):1762-73. DOI: 10.1038/emboj.2010.50
Source: PubMed

ABSTRACT Upon infection with many RNA viruses, the cytoplasmic retinoic acid inducible gene-I (RIG-I) pathway activates the latent transcription factor IRF-3, causing its nuclear translocation and the induction of many antiviral genes, including those encoding interferons. Here, we report a novel and distinct activity of IRF-3, in virus-infected cells, that induces apoptosis. Using genetically defective mouse and human cell lines, we demonstrated that, although both pathways required the presence of RIG-I, IPS1, TRAF3 and TBK1, only the apoptotic pathway required the presence of TRAF2 and TRAF6 in addition. More importantly, transcriptionally inactive IRF-3 mutants, such as the one missing its DNA-binding domain, could efficiently mediate apoptosis. Apoptosis was triggered by the direct interaction of IRF-3, through a newly identified BH3 domain, with the pro-apoptotic protein Bax, their co-translocation to the mitochondria and the resulting activation of the mitochondrial apoptotic pathway. Thus, IRF-3 is a dual-action cytoplasmic protein that, upon activation, translocates to the nucleus or to the mitochondrion and triggers two complementary antiviral responses of the infected cell.

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