title: A cypovirus VP5 displays the RNA chaperone-like activity that destabilizes RNA helices and accelerates strand annealing.
abstract: For double-stranded RNA (dsRNA) viruses in the family Reoviridae, their inner capsids function as the machinery for viral RNA (vRNA) replication. Unlike other multishelled reoviruses, cypovirus has a single-layered capsid, thereby representing a simplified model for studying vRNA replication of reoviruses. VP5 is one of the three major cypovirus capsid proteins and functions as a clamp protein to stabilize cypovirus capsid. Here, we expressed VP5 from type 5 Helicoverpa armigera cypovirus (HaCPV-5) in a eukaryotic system and determined that this VP5 possesses RNA chaperone-like activity, which destabilizes RNA helices and accelerates strand annealing independent of ATP. Our further characterization of VP5 revealed that its helix-destabilizing activity is RNA specific, lacks directionality and could be inhibited by divalent ions, such as Mg(2+), Mn(2+), Ca(2+) or Zn(2+), to varying degrees. Furthermore, we found that HaCPV-5 VP5 facilitates the replication initiation of an alternative polymerase (i.e. reverse transcriptase) through a panhandle-structured RNA template, which mimics the 5'-3' cyclization of cypoviral positive-stranded RNA. Given that the replication of negative-stranded vRNA on the positive-stranded vRNA template necessitates the dissociation of the 5'-3' panhandle, the RNA chaperone activity of VP5 may play a direct role in the initiation of reoviral dsRNA synthesis.
authors: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China and Department of Biochemistry, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China.
authors: Jie
authors: J
authors: Yang
authors: Zhenyun
authors: Z
authors: Cheng
authors: Songliu
authors: S
authors: Zhang
authors: Wei
authors: W
authors: Xiong
authors: Hongjie
authors: H
authors: Xia
authors: Yang
authors: Y
authors: Qiu
authors: Zhaowei
authors: Z
authors: Wang
authors: Feige
authors: F
authors: Wu
authors: Cheng-Feng
authors: CF
authors: Qin
authors: Lei
authors: L
authors: Yin
authors: Yuanyang
authors: Y
authors: Hu
authors: Xi
authors: X
authors: Zhou
mesh_terms: D000595:Amino Acid Sequence; D036022:Capsid Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012367:RNA, Viral / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D012087:Reoviridae / Q000235:genetics* / Q000378:metabolism; D048348:Reverse Transcription; D016415:Sequence Alignment
chemical_list: D036022:Capsid Proteins; D012367:RNA, Viral; D016601:RNA-Binding Proteins