Disease relevance of N

• The nucleocapsid (N) protein plays an essential role in SARS-CoV genome packaging and virion assembly [1].
• This finding provides structural evidence of the evolutionary link between Coronaviridae and Arteriviridae, suggesting that the N proteins of both viruses have a common origin [1].
• The Alb4 mutant of the coronavirus mouse hepatitis virus (MHV) is both temperature sensitive and thermolabile owing to a deletion in the gene encoding its nucleocapsid (N) protein [2].
• Targeted RNA recombination was used to construct mouse hepatitis virus (MHV) mutants containing chimeric nucleocapsid (N) protein genes in which segments of the bovine coronavirus N gene were substituted in place of their corresponding MHV sequences [3].
• The severe acute respiratory syndrome coronavirus(SARS-CoV) nucleocapsid (N) protein is one of the four structural proteins of the virus and is predicted to be a 46-kDa phosphoprotein [4].

High impact information on N

• The nucleocapsid-independent formation of apparently bona fide viral envelopes represents a novel mode of virus assembly [5].
• The nucleocapsid protein N is synthesized on free polysomes, whereas the envelope glycoproteins E1 and E2 are translated on the rough endoplasmic reticulum (RER) [6].
• In absence of S, expression of M and E or the nucleocapsid protein N did not induce a detectable serum SARS-CoV-neutralizing antibody response [7].
• Crystal structure of the severe acute respiratory syndrome (SARS) coronavirus nucleocapsid protein dimerization domain reveals evolutionary linkage between corona- and arteriviridae [1].
• Although lacking significant sequence similarity, the dimerization domain of SARS-CoV N protein has a fold similar to that of the nucleocapsid protein of the porcine reproductive and respiratory syndrome virus [1].

Chemical compound and disease context of N

• Neutralizing and nonneutralizing monoclonal antibodies to the peplomer glycoprotein and nucleocapsid protein of a mouse hepatitis virus (MHV), MHV-NuU, protected mice against lethal MHV-2 challenge [8].
• The two envelope glycoproteins and the viral nucleocapsid of the coronavirus A59 were isolated by solubilization of the viral membrane with Nonidet P-40 at 4 degrees C followed by sucrose density gradient sedimentation [9].
• The SARS-CoV nucleocapsid protein (N), three N fragments (N1, N2, and N3) and the intraviral domain of the membrane protein (M2) were cloned and expressed in Escherichia coli as histidine-tagged proteins [10].
• A Western immunoblot assay for confirmatory serodiagnosis of severe acute respiratory syndrome (SARS) was developed utilizing viral lysate antigens combined with a recombinant nucleocapsid protein, GST-N (glutathione S-transferase-nucleocapsid) of the SARS coronavirus (SARS-CoV) [11].

Biological context of N

• When M and N expression plasmids were cotransfected into human 293 renal epithelial cells, pseudoparticles formed readily [12].
• This provided a clear genetic proof that the Alb4 phenotype was due to the observed deletion in the N gene [13].
• This internal gene (designated I) is in the +1 reading frame with respect to the N gene, and it encodes a mostly hydrophobic 23-kDa polypeptide [14].
• The nucleocapsid (N) protein of several members within the order Nidovirales localizes to the nucleolus during infection and after transfection of cells with N genes [15].
• Initially, a 19-nucleotide tag was inserted into the start of gene 4a of MHV strain A59 with the N gene deletion mutant Alb4 as the recipient virus [16].

Anatomical context of N

• Recombinant VV encoding N protein (VV-N) induces a humoral and a CD4+ T cell response, but did not prevent acute disease regardless of the immunization protocol [17].
• These data provide the first definition of a MHV-specific CTL response directed to a viral protein and suggest that the anti-N protein CTL response is one potential mechanism used by the host to clear JHMV from the central nervous system [18].
• In the present study, the influence of small interfering RNA (siRNA) on SARS-CoV nucleocapsid (N) protein expression was detected in cultured cells and mouse muscles [19].
• By 8 to 12 h p.i., however, the membranes containing helicase and N had a predominantly perinuclear distribution and colocalized with M [20].
• In clinical samples the median concentrations of R- and N-gene RNA, respectively, were 1.2 x 10(6) and 2.8 x 10(6) copies/ml (sputum and endotracheal aspirates), 4.3 x 10(4) and 5.5 x 10(4) copies/ml (stool), and 5.5 x 10(2) and 5.2 x 10(2) copies/sample (throat swabs and saliva) [21].

Associations of N with chemical compounds

• BCV is a prototype for the coronaviruses that express an additional major structural protein, the hemagglutinin esterase (HE), in addition to the spike (S) glycoprotein, membrane (M) glycoprotein, and nucleocapsid (N) protein [22].
• In contrast, mutation of amino acid Gln-74 to an alanine, which does not affect the binding activity of the N-terminal domain, showed minimal, if any, detrimental effect on the infectivity of IBV [23].
• To distinguish between immune and replication associated mechanisms of persistence, brains from acutely and persistently infected mice were analyzed for viral RNA mutations in the encapsidation sequence (ECS) and regions encoding either the transmembrane domains of the matrix (M) protein or a protective CTL epitope in the nucleocapsid (N) protein [24].
• From the predicted sequence it was apparent that the nucleocapsid protein has 5 basic regions, two of which are located near the middle of the sequence, a serine-rich region was also located, a feature which may be of functional importance as the nucleocapsid protein is phosphorylated at serine residues [25].
• Incubation of the Nonidet P-40-disrupted virus at 37 degrees C resulted in formation of a complex between one of the viral glycoproteins, E1, and the viral nucleocapsid [9].

Analytical, diagnostic and therapeutic context of N

• Sequence analysis of the N genes of the revertants revealed that each contained a single second-site point mutation that compensated for the effects of the deletion [2].
• The results obtained by both Western blot and ELISA for binding to the truncated N proteins coincide for seven of the Mab tested [26].
• The nucleocapsid (N) protein of SARS-associated coronavirus (SARS-CoV) is abundantly expressed in infected-cell culture filtrate as demonstrable by Western blotting using convalescent-phase sera from patients with SARS [27].
• Northern blot analysis was performed to demonstrate differences in subgenomic transcripts of the virus, and a real-time quantitative PCR was employed to compare the sensitivities of two loci (1b and N) [28].
• Lysosomal trafficking of the LAMP/N chimera in transfected cells was documented by both confocal and immunoelectron microscopy [29].

References