Structural And Functional Investigation Of Junin Virus Nucleoprotein

Junin virus (JUNV) has been identified as the etiological agent of Argentine hemorrhagic fever (AHF), which is a serious public health problem with approximately5million people at risk. It is treated as a potential bioterrorism agent because of its rapid transmission by aerosols. JUNV is a negative-sense single-stranded RNA (-ssRNA) virus that belongs to the genus Arenavirus within the family Arenaviridae, and its genomic RNA contains two segments encoding four proteins. Among these, the nucleoprotein (NP) has essential roles in viral RNA synthesis and immune suppression, but the molecular mechanisms of its actions are only partially understood. To date, several NP structures of-ssRNA viruses have been reported but the only structure in the family Arenaviridae is the Lassa fever virus (LASV) NP. Here, we determined a2.2A crystal structure of the C-terminal domain of JUNV NP. This structure showed high similarity to the LASV NP C-terminal domain. However, both the structure and function of JUNV NP showed differences compared with LASV NP. This study extends our structural insight into the-ssRNA virus NPs.SARS-coronavirus has been identified as the etiological agent of a SARS (Severe Acute Respiratory Syndrom) outbreak spreading over the world in2003. This coronavirus could generate sixteen nonstructural proteins for the replication and transcription of the virus genome. Among these proteins, nonstructural protein8(nsp8) is a second RNA-dependent RNA polymerase (RdRp) that produces primers utilized by nsp12which is considered to be the canonical RdRp for SARS coronavirus. SARS coronavirus nonstructural proteins7(nsp7) and8(nsp8) form a primase supercomplex which is a unique structure implicating a distinctive mechanism of RdRp in coronaviruses. Here, we confirmed that the proteolysis product of nsp8contains the globular domain-nsp8C, and indentified the resection site that is notably conserved in coronaviruses. We subsequently crystallized the complex of SARS-CoV nsp8C and nsp7, and the3-D structure of this domain revealed its capability to interfuse into the hexadecamer supercomplex. This specific proteolysis may indicate one possible mechanism by which coronaviruses switch from viral infection to genome replication and viral assembly stages.