Disease relevance of NP

• The product nucleocapsids formed with three mutants, NP114, NP121, and NP126, however, did not serve as templates for further amplification in vivo, while NP107, NP108, and NP111 were nearly like wild-type NP in vivo [1].
• The Sendai virus V protein interacts with the NP protein to regulate viral genome RNA replication [2].
• This truncated NP protein was identified in cells naturally infected with the defective virus preparation [3].
• We have shown that the measles virus nucleocapsid protein, N, can substitute for the Sendai NP protein in genome synthesis [4].
• An RNA-dependent RNA polymerase (L and P protein) is packaged within the virion which faithfully copies the genome RNA in vitro and in vivo; this enzyme complex, in association with the nucleocapsid protein (N), is also involved in the replication process [5].

High impact information on NP

• FL-3 was marked with a BglII site in the leader region and an NsiI site (ATGCAT) in the 5' nontranslated region of the NP gene, creating a new, out-of-frame, 5' proximal AUG. All the virus stocks generated eventually removed this impediment to NP expression, by either point mutation or recombination between FL-3 and pGEM-NP [6].
• When BHK-21 cells with Semliki Forest virus (SFV) bound at the plasma membrane are briefly treated with low pH medium (pH 5-6), fusion between the viral membrane and the plasma membrane occurs, releasing the viral nucleocapsid into the cytoplasm [7].
• This study describes an analysis of the interaction of individual amino acid residues of the vesicular stomatitis virus (VSV) nucleocapsid antigenic octapeptide (N52-59; Arg-Gly-Tyr-Val-Tyr-Gln-Gly-Leu) with the H-2Kb molecule and T-cell receptors (TCRs) [8].
• Proteolysis with trypsin, chymotrypsin, or Pronase, which digests only the external surface of the IO vesicles (the cytoplasmic surface of the erythrocyte membrane) revealed that the viral nucleocapsid and the nonglycosylated inner-envelope (M) proteins were present on the external surface [9].
• The results indicated that 6 M guanidine, 40 mM lithium diiodosalicylate (pH 11-13), and 4 M potassium thiocyanate removed viral nucleocapsid and M proteins from the vesicles [10].

Chemical compound and disease context of NP

• By the use of horseradish peroxidase-labelled Fab fragments of monoclonal antibodies, five major structural components of Sendai virus, namely the nucleocapsid (NP), polymerase (P), matrix (M), fusion (F), and haemagglutinin-neuraminidase (HN) proteins were localized in infected Vero cells [11].
• Alanine substitution mutations in the Sendai virus nucleocapsid (NP) protein have defined highly conserved hydrophobic and charged residues from amino acids (aa) 362 to 371 that are essential for function of the protein in RNA replication [12].
• Alteration of Sendai virus morphogenesis and nucleocapsid incorporation due to mutation of cysteine residues of the matrix protein [13].
• Using a detergent and high salt solubilization procedure, the protein kinase activity was found associated within glycoprotein free virus particles but not with the nucleocapsid-associated polypeptides [14].
• The alteration of whole Sendai virus and especially of its nucleocapsid polypeptides, during storage of the virus at 4 degree C in the allantoic fluids in which it was cultivated, has cultivated, has been studied by sodium dodecyl sulfate gel electrophoresis [15].

Biological context of NP

• We propose that amino acids 114 to 129 of the NP protein are required for the nucleocapsid to function as a template in viral genome replication [1].
• To identify domains in the NP protein, mutants were constructed by using clustered charge-to-alanine mutagenesis in a highly charged region from amino acids 107 to 129 [1].
• Previous studies showed that the C-terminal 124 amino acids of NP (aa 401-524) contain the P-NC binding site [16].
• A natural Sendai virus internal deletion defective interfering (DI) RNA, previously shown to encode a truncated NP protein and previously cloned under the control of the T7 RNA polymerase promoter, was expressed from plasmid and shown to replicate in cell tissue culture when the viral proteins NP, P, and L were coexpressed from cloned genes [17].
• The data suggest that the L and NP protein-binding domains on P protein do not overlap [18].

Anatomical context of NP

• This result demonstrates that it is possible to stably express adequate levels of all three viral NC proteins to form Sendai virus polymerase activity, thereby performing the replication and encapsidation of viral RNA, essential prerequisites for a helper cell line to be competent in producing recombinant viruses [19].
• Coexpression of the NP and P proteins resulted in the accumulation of large cytoplasmic inclusion aggregates, similar to those visualized at late times in SV5-infected cells [20].
• The properties of these cell lines, in terms of the induction of the P, V, and NP genes, are described in detail [20].
• NP molecules were found uniformly along the entire length of both cytosol and virion derived nucleocapsids [21].
• Additionally, the L, P and NP proteins, which were associated with the plasma membrane isolated from the infected cells maintained at permissive temperature, were absent from the membrane of cells incubated at non-permissive temperature [22].

Associations of NP with chemical compounds

• Mutant L proteins with basic arginine or histidine substitutions were inactive in all viral RNA synthesis in vitro, although the polymerase complexes could bind the nucleocapsid template [23].
• The epitopes found were six for the HN, two for the F, six for the NP and six for the M protein [24].
• Urea (6.0 M) and 5 mM p-chloromercuribenzenesulfonate removed only viral nucleocapsid proteins [10].
• These results indicate that a single-point mutation at a cysteine residue of the M protein affects virus morphology and nucleocapsid incorporation, showing direct involvement of the M protein in SeV assembly [13].
• The results indicated that SV5 DI RNA replication was reduced by substitutions for two CG dinucleotides, which in the nucleocapsid template are in the first two positions of the first two hexamers of CRII nucleotides [25].

Other interactions of NP

• Using the two-hybrid system we have confirmed the previously identified P-L (RNA polymerase), NPo-P (encapsidation substrate), and P-P complexes and now demonstrate NP-NP and NPo-V protein interactions [2].
• In addition, the abnormal virus-like particles, of which HN protein and nucleocapsid were ablated, were released in the culture medium at 41 degrees C, although the size was smaller than the normal viral virions [26].

Analytical, diagnostic and therapeutic context of NP

• Baculovirus recombinants containing the NP gene were identified by PCR [27].
• Previous sequence analyses of these mutant RNAs suggested that all four possessed the transcription initiation signal of the NP gene and the transcription termination signal of the L gene [28].
• Complementary studies involving site-directed mutagenesis of the full-length NP protein have identified specific residues in the CCR which are essential for viral RNA replication in vitro [29].
• Immunofluorescence analysis supported this data showing that at later times p.i., although there were some cells which were positive for all the viral proteins, a high proportion of cells were strongly positive for NP and P but negative for M, F and HN proteins [30].
• Using SDS-PAGE and immunoblotting with a novel phosphospecific antibody, we show for the first time that, in vivo, IRF-3 is phosphorylated on Ser(396) following Sendai virus infection, expression of viral nucleocapsid, and double-stranded RNA treatment [31].

References