Disease relevance of SH2D3C

• The Chinese adult diarrhea rotavirus (ADRV) and the Indian CAL strains of human group B rotaviruses were reported to be conserved in genes encoding structural proteins but divergent in NSP2 and NSP3 genes, raising the questions about the origin and the evolution of these strains [1].
• Here, we identify SARS coronavirus amino-terminal replicase products nsp1, nsp2, and nsp3 and describe trans-cleavage assays that characterize the protease activity required to generate these products [2].
• Expression of two bovine rotavirus non-structural proteins (NSP2, NSP3) in the baculovirus system and production of monoclonal antibodies directed against the expressed proteins [3].
• Rotaviruses, segmented double-stranded RNA viruses, co-opt the eukaryotic translation machinery with the aid of nonstructural protein 3 (NSP3), a rotaviral functional homolog of the cellular poly(A) binding protein (PABP) [4].
• NSP3 products expressed in COS-1 cells were capable of inhibiting activation of the double-stranded RNA-dependent protein kinase similar to other double-stranded RNA-binding proteins, and NSP3 products expressed in HeLa cells were capable of rescuing the replication of an interferon-sensitive deletion mutant of vaccinia virus [5].

High impact information on SH2D3C

• Rotaviruses, the cause of life-threatening diarrhea in humans and cattle, utilize a functional homolog of poly(A) binding protein (PABP) known as nonstructural protein 3 (NSP3) for translation of viral mRNAs [6].
• NSP3 binds to viral mRNA 3' consensus sequences and circularizes the mRNA via interactions with eIF4G [6].
• Biophysical studies demonstrate high affinity binding leading to increased thermal stability and slow dissociation kinetics, consistent with NSP3 function [6].
• Genome analysis also revealed various numbers of tandem copies of a perfect 30-base acidic tandem repeat (ATR) which encodes NDDEDVVTGD and various numbers and sequences of imperfect repeats in the N terminus of nsp3 inside the acidic domain upstream of papain-like protease 1 among the 22 genomes [7].
• In contrast, processing at the nsp2/3 site is less efficient, since a approximately 300-kDa intermediate (NSP2-3) is detected, but ultimately nsp2 (p71) and nsp3 (p213) are generated [2].

Biological context of SH2D3C

• These data support the hypothesis that NSP3, coded for by genome segment 7, plays a significant role in viral growth in the gut and spread to peripheral sites [8].
• The mechanism of NSP3-mediated tropism is under investigation [8].
• A human rotavirus with rearranged genes 7 and 11 encodes a modified NSP3 protein and suggests an additional mechanism for gene rearrangement [9].
• This effect was abolished by deletions in the eIF4G-binding (aa 274-313) and the dimerization (aa 150-206) but not the viral mRNA-binding (aa 83-149) domains, supporting that NSP3 functions in vivo as a dimer [10].

Anatomical context of SH2D3C

• To make such reagents available, we have expressed in the baculovirus system NSP2 and NSP3 (formerly called NS35 and NS34, respectively) of the bovine rotavirus RF and produced hybridomas against these proteins [3].
• A clone of NSP3, expressed both in vitro and in COS-1 cells, led to the synthesis of minor amounts of a product with an M(r) of 45,000 (the expected full-length M(r) of NSP3) and major amounts of products with M(r)s of 38,000 and 8,000 [5].
• A recombinant vaccinia virus encoding rotavirus protein NSP3 driven by an internal ribosome entry site (IRES) from the encephalomyocarditis (EMC) virus was able to abate protein synthesis in BSC1 cells by 25-fold, with as much as 30% of the remaining protein synthesis being NSP3 [10].

Analytical, diagnostic and therapeutic context of SH2D3C

• The levels of synthesis and cellular localization of NSP3 and NSP2 proteins were different as shown by immunoprecipitation and immunofluorescence [3].
• Site-directed mutagenesis and isothermal titration calorimetry documented that NSP3 and PABP use analogous eIF4G recognition strategies, despite marked differences in tertiary structure [4].
• A fragment of 87 bp in a highly-conserved region of non-structural protein 3 (NSP3) in rotavirus genome was amplified by a single-step RT-PCR protocol in a closed-tube system [11].

References