Essential role of hyperacetylated microtubules in innate immunity escape orchestrated by the EBV-encoded BHRF1 protein

Abstract Innate immunity constitutes the first line of defense against viruses, in which mitochondria play an important role in the induction of the interferon (IFN) response. BHRF1, a multifunctional viral protein expressed during Epstein-Barr virus reactivation, modulates mitochondrial dynamics and disrupts the IFN signaling pathway. Mitochondria are mobile organelles that move through the cytoplasm thanks to the cytoskeleton and in particular the microtubule (MT) network. MTs undergo various post-translational modifications, among them tubulin acetylation. In this study, we demonstrated that BHRF1 induces MT hyperacetylation to escape innate immunity. Indeed, expression of BHRF1 induces the aggregation of shortened mitochondria next to the nucleus. This mito-aggresome is organized around the centrosome and its formation is MT-dependent. We also observed that the BHRF1-induced hyperacetylation of MTs involves the α-tubulin acetyltransferase ATAT1. Thanks to a non-acetylatable α-tubulin mutant, we demonstrated that this hyperacetylation is necessary for the mito-aggresome formation. We investigated the mechanism leading to the clustering of mitochondria, and we identified dyneins as motors that are required for the mitochondrial aggregation. Finally, we demonstrated that BHRF1 needs MT hyperacetylation to block the induction of the IFN response. Indeed, in the absence of MT hyperacetylation, BHRF1 is unable to initiate the sequestration of mitochondria into autophagosomes, and mitophagy, which is essential to inhibiting the signaling pathway. Therefore, our results reveal the role of the MT network, and its acetylation level, in the induction of a pro-viral mitophagy.