Sin Nombre Virus (SNV) is a member of the hantavirus genus in the Bunyaviridae family. Hantaviruses contain a tripartite negative sense RNA genome with individual segments that form panhandle structures through intramolecular interaction between the 5 and 3' termini. This panhandle structure is recognized at high affinity by trimeric viral nucleocapsid protein (N), and this interaction is likely to be important for specific encapsidation of viral RNA (vRNA) into nucleoprotein complexes in cells, for incorporation of vRNA into assembling virus particles, and for initiation of genomic vRNA replication. N is also capable of unwinding RNA/RNA duplexes as an RNA chaperone. This function is critical for rescuing kinetically trapped misfolded RNAs. We examined the regions of N required for high affinity binding to the viral RNA panhandle and isolate the domain responsible for RNA helix unwinding using a set of mutations in the SNV N gene. These data indicate that components of both the N- and C-termini of the N are necessary and sufficient for vRNA panhandle recognition. It is possible to functionally replace the C-terminal region with a foreign trimerization domain, the T4 phage fibritin domain, and maintain high affinity binding. Thus, N trimerization, mediated by the C-terminus, in conjunction with a putative RNA binding site in the N-terminus, appears to be required for panhandle recognition. In contrast, the RNA chaperone function is not dependent on trimer formation. The domain responsible for RNA helix destabilization resides within the putative disordered region of the N-terminal 100 amino acids of N. Surprisingly, rescue of trimer formation with the addition of the T4 fibritin domain abolishes RNA chaperone activity. We demonstrate here that the N-terminus of SNV N facilitates both high affinity vRNA binding and RNA chaperone activity.
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Biomedical Sciences Graduate Program
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Brown, Bradley. "The RNA binding and RNA chaperone activity of Sin Nombre virus nucleocapsid." (2008). http://digitalrepository.unm.edu/biom_etds/102