Chunyan Han, Xiangwei Zeng , Shuai Yao Li Gao , Lizhou Zhang , Xiaole Qi , Yulu Duan , Bo Yang, Yulong Gao , Changjun Liu , Yanping Zhang , Yongqiang Wang*, Xiaomei Wang*

J Virol. 2017 Jun 7. pii: JVI.00584-17

Abstract

Infectious bursal disease virus (IBDV) is a double-stranded RNA virus. Segment A contains two overlapping open reading frames (ORFs), which encode viral proteins VP2, VP3, VP4, and VP5. Segment B contains one ORF and encodes the viral RNA-dependent RNA polymerase, VP1. IBDV ribonucleoprotein complexes are composed of VP1, VP3, and dsRNA and play a critical role in mediating viral replication and transcription during virus life cycles. Here, we identified a cellular factor, VDAC1, which was upregulated during IBDV infection and found to mediate IBDV polymerase activity. VDAC1 senses IBDV infection by interacting with viral proteins VP1 and VP3. This association is caused by RNA bridging and all three proteins co-localise in the cytoplasm. Furthermore, small interfering RNA (siRNA)-mediated downregulation of VDAC1 resulted in a reduction in viral polymerase activity and a subsequent decrease in viral yield. Moreover, overexpression of VDAC1 enhances IBDV polymerase activity. We also found that viral protein VP3 can replace segment A to execute polymerase activity. A previous study showed that mutations in the C-terminus of VP3 directly influence the formation of VP1-VP3 complexes. Our immunoprecipitation experiments demonstrated that protein-protein interactions between VDAC1 and VP3 and between VDAC1 and VP1 play a role in stabilising the interaction between VP3 and VP1, further promoting IBDV polymerase activity.IMPORTANCE The cellular factor VDAC1 controls the entry and exit of mitochondrial metabolites and plays a pivotal role during intrinsic apoptosis by mediating the release of many apoptogenic molecules. Here, we identify a novel role of VDAC1, showing that VDAC1 interacts with IBDV ribonucleoproteins (RNPs) and facilitates IBDV replication by enhancing IBDV polymerase activity through its ability to stabilise interactions in RNP complexes. To our knowledge, this is the first report that VDAC1 is specifically involved in regulating IBDV RNA polymerase activity, providing novel insight into virus-host interactions.