title: Structural basis for dimerization and RNA binding of avian infectious bronchitis virus nsp9.
abstract: The potential for infection by coronaviruses (CoVs) has become a serious concern with the recent emergence of Middle East respiratory syndrome and severe acute respiratory syndrome (SARS) in the human population. CoVs encode two large polyproteins, which are then processed into 15-16 nonstructural proteins (nsps) that make significant contributions to viral replication and transcription by assembling the RNA replicase complex. Among them, nsp9 plays an essential role in viral replication by forming a homodimer that binds single-stranded RNA. Thus, disrupting nsp9 dimerization is a potential anti-CoV therapy. However, different nsp9 dimer forms have been reported for alpha- and beta-CoVs, and no structural information is available for gamma-CoVs. Here we determined the crystal structure of nsp9 from the avian infectious bronchitis virus (IBV), a representative gamma-CoV that affects the economy of the poultry industry because it can infect domestic fowl. IBV nsp9 forms a homodimer via interactions across a hydrophobic interface, which consists of two parallel alpha helices near the carboxy terminus of the protein. The IBV nsp9 dimer resembles that of SARS-CoV nsp9, indicating that this type of dimerization is conserved among all CoVs. This makes disruption of the dimeric interface an excellent strategy for developing anti-CoV therapies. To facilitate this effort, we characterized the roles of six conserved residues on this interface using site-directed mutagenesis and a multitude of biochemical and biophysical methods. We found that three residues are critical for nsp9 dimerization and its abitlity to bind RNA.
authors.affiliation: State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, 610041, P.R. China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Hu
authors.affiliation: School of Life Sciences, Tianjin University, Tianjin, 300072, P.R. China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, 610041, P.R. China.
authors.forename: Huiyan
authors.initials: H
authors.lastname: Li
authors.affiliation: State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, 610041, P.R. China.
authors.forename: Yanshu
authors.initials: Y
authors.lastname: Dou
authors.affiliation: State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, 610041, P.R. China.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, 610041, P.R. China.
authors.forename: Deren
authors.initials: D
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, 610041, P.R. China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zong
authors.affiliation: Department of Organic Chemistry, School of Pharmacy, Second Military Medical University, Shanghai, 200433, P.R. China.
authors.forename: Yulei
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Chemistry, Sichuan University, Chengdu, 610041, P.R. China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Yang
authors.affiliation: Laboratory of Non-human Primate Disease Modeling Research, West China Hospital, Sichuan University, Chengdu, 610041, P.R. China.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Zhong
authors.affiliation: Ludwig Institute for Cancer Research, University of California, La Jolla, San Diego, California, 92093, USA.
authors.forename: Namit
authors.initials: N
authors.lastname: Singh
authors.affiliation: Department of Organic Chemistry, School of Pharmacy, Second Military Medical University, Shanghai, 200433, P.R. China.
authors.forename: Honggang
authors.initials: H
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, 610041, P.R. China.|Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, 610041, P.R. China.
authors.forename: Rundong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: School of Life Sciences, Tianjin University, Tianjin, 300072, P.R. China.
authors.forename: Haitao
authors.initials: H
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, 610041, P.R. China.
authors.forename: Dan
authors.initials: D
authors.lastname: Su
mesh_terms: D001351:Infectious bronchitis virus / Q000737:chemistry* / Q000378:metabolism; D055503:Protein Multimerization; D012367:RNA, Viral / Q000737:chemistry* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D012367:RNA, Viral; D016601:RNA-Binding Proteins; D014764:Viral Proteins
keywords: Nsp9; coronaviruses; dimerization; infectious bronchitis virus; nonstructural proteins