scholarly journals Recombinant SARS-CoV-2 Nucleocapsid Protein: Expression, Purification, and Its Biochemical Characterization and Utility in Serological Assay Development to Assess Immunological Responses to SARS-CoV-2 Infection

Pathogens ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1039
Author(s):  
Da Di ◽  
Mythili Dileepan ◽  
Shamim Ahmed ◽  
Yuying Liang ◽  
Hinh Ly
Keyword(s):  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Biochemical Characterization ◽  
Free Form ◽  
Bacterial Cells ◽  
Serum Samples ◽  
Mobility Shift ◽  
Independent Manner ◽  
Serological Assay ◽  
Terminal Domain

The SARS-CoV-2 nucleocapsid protein (N) binds a single-stranded viral RNA genome to form a helical ribonucleoprotein complex that is packaged into virion particles. N is relatively conserved among coronaviruses and consists of the N-terminal domain (NTD) and C-terminal domain (CTD), which are flanked by three disorganized regions. N is highly immunogenic and has been widely used to develop a serological assay as a diagnostic tool for COVID-19 infection, although there is a concern that the natural propensity of N to associate with RNA might compromise the assay’s specificity. We expressed and purified from bacterial cells two recombinant forms of SARS-CoV-2 N, one from the soluble fraction of bacterial cell lysates that is strongly associated with bacterial RNAs and the other that is completely devoid of RNAs. We showed that both forms of N can be used to develop enzyme-linked immunosorbent assays (ELISAs) for the specific detection of human and mouse anti-N monoclonal antibodies (mAb) as well as feline SARS-CoV-2 seropositive serum samples, but that the RNA-free form of N exhibits a slightly higher level of sensitivity than the RNA-bound form to react to anti-N mouse mAb. Using the electrophoretic mobility shift assay (EMSA), we also showed that N preferentially binds ssRNA in a sequence-independent manner and that both NTD and CTD of N contribute to RNA-binding activity. Collectively, our study describes methods to express, purify, and biochemically characterize the SARS-CoV-2 N protein and to use it for the development of serological assays to detect SARS-CoV-2 infection.

scholarly journals Characterization of the RNA-Binding Domains in the Replicase Proteins of Tomato Bushy Stunt Virus

2003 ◽  
Vol 77 (17) ◽  
pp. 9244-9258 ◽  
Author(s):  
K. S. Rajendran ◽  
Peter D. Nagy
Keyword(s):  
Rna Binding ◽  
Tomato Bushy Stunt Virus ◽  
Binding Motif ◽  
Mobility Shift ◽  
Terminal Domain ◽  
Binding Domains ◽  
Replicase Proteins ◽  
Rna Binding Domains ◽  
Gel Mobility Shift

ABSTRACT Tomato bushy stunt virus (TBSV), a tombusvirus with a nonsegmented, plus-stranded RNA genome, codes for two essential replicase proteins. The sequence of one of the replicase proteins, namely p33, overlaps with the N-terminal domain of p92, which contains the signature motifs of RNA-dependent RNA polymerases (RdRps) in its nonoverlapping C-terminal portion. In this work, we demonstrate that both replicase proteins bind to RNA in vitro based on gel mobility shift and surface plasmon resonance measurements. We also show evidence that the binding of p33 to single-stranded RNA (ssRNA) is stronger than binding to double-stranded RNA (dsRNA), ssDNA, or dsDNA in vitro. Competition experiments with ssRNA revealed that p33 binds to a TBSV-derived sequence with higher affinity than to other nonviral ssRNA sequences. Additional studies revealed that p33 could bind to RNA in a cooperative manner. Using deletion derivatives of the Escherichia coli-expressed recombinant proteins in gel mobility shift and Northwestern assays, we demonstrate that p33 and the overlapping domain of p92, based on its sequence identity with p33, contain an arginine- and proline-rich RNA-binding motif (termed RPR, which has the sequence RPRRRP). This motif is highly conserved among tombusviruses and related carmoviruses, and it is similar to the arginine-rich motif present in the Tat trans-activator protein of human immunodeficiency virus type 1. We also find that the nonoverlapping C-terminal domain of p92 contains additional RNA-binding regions. Interestingly, the location of one of the RNA-binding domains in p92 is similar to the RNA-binding domain of the NS5B RdRp protein of hepatitis C virus.

scholarly journals Crystallographic analysis of the N-terminal domain ofMiddle East respiratory syndrome coronavirusnucleocapsid protein

2015 ◽  
Vol 71 (8) ◽  
pp. 977-980 ◽  
Author(s):  
Yong-Sheng Wang ◽  
Chung-ke Chang ◽  
Ming-Hon Hou
Keyword(s):  
Molecular Weight ◽  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Crystallographic Analysis ◽  
Asymmetric Unit ◽  
Unit Cell Parameters ◽  
Data Set ◽  
Cell Parameters ◽  
Terminal Domain ◽  
Positively Charged

The N-terminal domain of the nucleocapsid protein fromMiddle East respiratory syndrome coronavirus(MERS-CoV NP-NTD) contains many positively charged residues and has been identified to be responsible for RNA binding during ribonucleocapsid formation by the virus. In this study, the crystallization and crystallographic analysis of MERS-CoV NP-NTD (amino acids 39–165), with a molecular weight of 14.7 kDa, are reported. MERS-CoV NP-NTD was crystallized at 293 K using PEG 3350 as a precipitant and a 94.5% complete native data set was collected from a cooled crystal at 77 K to 2.63 Å resolution with an overallRmergeof 9.6%. The crystals were monoclinic and belonged to space groupP21, with unit-cell parametersa= 35.60,b= 109.64,c = 91.99 Å, β = 101.22°. The asymmetric unit contained four MERS-CoV NP-NTD molecules.

scholarly journals Biochemical characterization of INTS3 and C9ORF80, two subunits of hNABP1/2 heterotrimeric complex in nucleic acid binding

2018 ◽  
Vol 475 (1) ◽  
pp. 45-60 ◽  
Author(s):  
Venkatasubramanian Vidhyasagar ◽  
Yujiong He ◽  
Manhong Guo ◽  
Tanu Talwar ◽  
Ravi Shankar Singh ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Rna Binding ◽  
Biochemical Characterization ◽  
Rna Binding Proteins ◽  
Gel Filtration ◽  
Anomalous Behavior ◽  
Random Coil ◽  
Nucleic Acid Binding ◽  
Mobility Shift ◽  
Dna And Rna

Human nucleic acid-binding protein 1 and 2 (hNABP1 and hNABP2, also known as hSSB2 and hSSB1 respectively) form two separate and independent complexes with two identical proteins, integrator complex subunit 3 (INTS3) and C9ORF80. We and other groups have demonstrated that hNABP1 and 2 are single-stranded (ss) DNA- and RNA-binding proteins, and function in DNA repair; however, the function of INTS3 and C9OFR80 remains elusive. In the present study, we purified recombinant proteins INTS3 and C9ORF80 to near homogeneity. Both proteins exist as a monomer in solution; however, C9ORF80 exhibits anomalous behavior on SDS–PAGE and gel filtration because of 48% random coil present in the protein. Using electrophoretic mobility shift assay (EMSA), INTS3 displays higher affinity toward ssRNA than ssDNA, and C9ORF80 binds ssDNA but not ssRNA. Neither of them binds dsDNA, dsRNA, or RNA : DNA hybrid. INTS3 requires minimum of 30 nucleotides, whereas C9OFR80 requires 20 nucleotides for its binding, which increased with the increasing length of ssDNA. Interestingly, our GST pulldown results suggest that the N-terminus of INTS3 is involved in protein–protein interaction, while EMSA implies that the C-terminus is required for nucleic acid binding. Furthermore, we purified the INTS3–hNABP1/2–C9ORF80 heterotrimeric complex. It exhibits weaker binding compared with the individual hNABP1/2; interestingly, the hNABP1 complex prefers ssDNA, whereas hNABP2 complex prefers ssRNA. Using reconstituted heterotrimeric complex from individual proteins, EMSA demonstrates that INTS3, but not C9ORF80, affects the nucleic acid-binding ability of hNABP1 and hNABP2, indicating that INTS3 might regulate hNABP1/2's biological function, while the role of C9ORF80 remains unknown.

scholarly journals Crystal structure of SARS-CoV-2 nucleocapsid protein RNA binding domain reveals potential unique drug targeting sites

2020 ◽  
Author(s):  
Sisi Kang ◽  
Mei Yang ◽  
Zhongsi Hong ◽  
Liping Zhang ◽  
Zhaoxia Huang ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Structural Information ◽  
Antiviral Drug ◽  
Binding Domain ◽  
Binding Studies ◽  
Terminal Domain ◽  
Rna Binding Domain

AbstractThe outbreak of coronavirus disease (COVID-19) in China caused by SARS-CoV-2 virus continually lead to worldwide human infections and deaths. It is currently no specific viral protein targeted therapeutics yet. Viral nucleocapsid protein is a potential antiviral drug target, serving multiple critical functions during the viral life cycle. However, the structural information of SARS-CoV-2 nucleocapsid protein is yet to be clear. Herein, we have determined the 2.7 Å crystal structure of the N-terminal RNA binding domain of SARS-CoV-2 nucleocapsid protein. Although overall structure is similar with other reported coronavirus nucleocapsid protein N-terminal domain, the surface electrostatic potential characteristics between them are distinct. Further comparison with mild virus type HCoV-OC43 equivalent domain demonstrates a unique potential RNA binding pocket alongside the β-sheet core. Complemented by in vitro binding studies, our data provide several atomic resolution features of SARS-CoV-2 nucleocapsid protein N-terminal domain, guiding the design of novel antiviral agents specific targeting to SARS-CoV-2.

scholarly journals The SARS-CoV-2 nucleocapsid protein preferentially binds long and structured RNAs

2021 ◽  
Author(s):  
Christen E Tai ◽  
Einav Tayeb-Fligelman ◽  
Sarah Griner ◽  
Lukasz Salwinski ◽  
Jeannette T Bowler ◽  
...  
Keyword(s):  
Nucleocapsid Protein ◽  
Amyloid Fibrils ◽  
Rna Binding ◽  
Low Complexity ◽  
Dimerization Domain ◽  
Mobility Shift ◽  
Genome Packaging ◽  
Biochemical Basis ◽  
Virion Assembly ◽  
Multiple Structures

The SARS-CoV-2 nucleocapsid protein (NCAP) functions in viral RNA genome packaging, virion assembly, RNA synthesis and translation, and regulation of host immune response. RNA-binding is central to these processes. Little is known how NCAP selects its binding partners in the myriad of host and viral RNAs. To address this fundamental question, we employed electrophoresis mobility shift and competition assays to compare NCAP binding to RNAs that are of SARS-CoV-2 vs. non-SARS-CoV-2, long vs. short, and structured vs. unstructured. We found that although NCAP can bind all RNAs tested, it primarily binds structured RNAs, and their association suppresses strong interaction with single-stranded RNAs. NCAP prefers long RNAs, especially those containing multiple structures separated by single-stranded linkers that presumably offer conformational flexibility. Additionally, all three major regions of NCAP bind RNA, including the low complexity domain and dimerization domain that promote formation of NCAP oligomers, amyloid fibrils and liquid-liquid phase separation. Combining these observations, we propose that NCAP-NCAP interactions that mediate higher-order structures during packaging also drive recognition of the genomic RNA and call this mechanism recognition-by-packaging. This study provides a biochemical basis for understanding the complex NCAP-RNA interactions in the viral life cycle and a broad range of similar biological processes.

scholarly journals Structure of the Paramyxovirus Parainfluenza Virus 5 Nucleoprotein in Complex with an Amino-Terminal Peptide of the Phosphoprotein

2017 ◽  
Vol 92 (5) ◽  
Author(s):  
Megha Aggarwal ◽  
George P. Leser ◽  
Christopher A. Kors ◽  
Robert A. Lamb
Keyword(s):  
Crystal Structure ◽  
Binding Site ◽  
Rna Binding ◽  
Hinge Region ◽  
Parainfluenza Virus ◽  
Free Form ◽  
Conformational Switching ◽  
Amino Terminal ◽  
Terminal Domain ◽  
Parainfluenza Virus 5

ABSTRACT Parainfluenza virus 5 (PIV5) belongs to the family Paramyxoviridae , which consists of enveloped viruses with a nonsegmented negative-strand RNA genome encapsidated by the nucleoprotein (N). Paramyxovirus replication is regulated by the phosphoprotein (P) through protein-protein interactions with N and the RNA polymerase (L). The chaperone activity of P is essential to maintain the unassembled RNA-free form of N in order to prevent nonspecific RNA binding and premature N oligomerization. Here, we determined the crystal structure of unassembled PIV5 N in complex with a P peptide (N 0 P) derived from the N terminus of P (P50) at 2.65 Å. The PIV5 N 0 P consists of two domains: an N-terminal domain (NTD) and a C-terminal domain (CTD) separated by a hinge region. The cleft at the hinge region of RNA-bound PIV5 N was previously shown to be an RNA binding site. The N 0 P structure shows that the P peptide binds to the CTD of N and extends toward the RNA binding site to inhibit N oligomerization and, hence, RNA binding. Binding of P peptide also keeps the PIV5 N in the open form. A molecular dynamics (MD) analysis of both the open and closed forms of N shows the flexibility of the CTD and the preference of the N protein to be in an open conformation. The gradual opening of the hinge region, to release the RNA, was also observed. Together, these results advance our knowledge of the conformational swapping of N required for the highly regulated paramyxovirus replication. IMPORTANCE Paramyxovirus replication is regulated by the interaction of P with N and L proteins. Here, we report the crystal structure of unassembled parainfluenza virus 5 (PIV5) N chaperoned with P peptide. Our results provide a detailed understanding of the binding of P to N. The conformational switching of N between closed and open forms during its initial interaction with P, as well as during RNA release, was analyzed. Our data also show the plasticity of the CTD and the importance of domain movement for conformational switching. The results improve our understanding of the mechanism of interchanging N conformations for RNA replication and release.

scholarly journals RNA Binding Properties of Bunyamwera Virus Nucleocapsid Protein and Selective Binding to an Element in the 5′ Terminus of the Negative-Sense S Segment

2000 ◽  
Vol 74 (21) ◽  
pp. 9946-9952 ◽  
Author(s):  
Jane C. Osborne ◽  
Richard M. Elliott
Keyword(s):  
Nucleocapsid Protein ◽  
Rna Binding ◽  
Metal Chelate ◽  
Rnase A ◽  
Mobility Shift ◽  
N Protein ◽  
Encapsidation Signal ◽  
Negative Sense ◽  
Bunyamwera Virus

ABSTRACT The genome of Bunyamwera virus (BUN) (familyBunyaviridae, genus Bunyavirus) comprises three negative-sense RNA segments which act as transcriptional templates for the viral polymerase only when encapsidated by the nucleocapsid protein (N). Previous studies have suggested that the encapsidation signal may reside within the 5′ terminus of each segment. The BUN N protein was expressed as a 6-histidine-tagged fusion protein in Escherichia coli and purified by metal chelate chromatography. An RNA probe containing the 5′-terminal 32 and 3′-terminal 33 bases of the BUN S (small) genome segment was used to investigate binding by the N protein in vitro using gel mobility shift and filter binding assays. On acrylamide gels a number of discrete RNA-N complexes were resolved, and analysis of filter binding data indicated a degree of cooperativity in N protein binding. RNA-N complexes were resistant to digestion with up to 1 μg of RNase A per ml. Competition assays with a variety of viral and nonviral RNAs identified a region within the 5′ terminus of the BUN S segment for which N had a high preference for binding. This site may constitute the signal for initiation of encapsidation by N.

scholarly journals Dynamic interactions between the RNA chaperone Hfq, small regulatory RNAs and mRNAs in live bacterial cells

2020 ◽  
Author(s):  
Seongjin Park ◽  
Karine Prévost ◽  
Emily M. Heideman ◽  
Marie-Claude Carrier ◽  
Matthew A. Reyer ◽  
...  
Keyword(s):  
Gene Regulation ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Normal Growth ◽  
Bacterial Cells ◽  
Rnase E ◽  
Independent Manner ◽  
Rna Chaperone ◽  
Mrna Binding

AbstractRNA binding proteins play myriad roles in controlling and regulating RNAs and RNA-mediated functions, often through simultaneous binding to other cellular factors. In bacteria, the RNA chaperone Hfq modulates post-transcriptional gene regulation. Absence of Hfq leads to the loss of fitness and compromises the virulence of bacterial pathogens. Using live-cell super-resolution imaging, we are able to distinguish Hfq binding to different sizes of cellular RNAs. We demonstrate that under normal growth conditions, Hfq exhibits widespread mRNA binding activity. Particularly, the distal face of Hfq contributes mostly to the mRNA binding in vivo. In addition, binding of Hfq to these mRNAs can recruit RNase E to promote turnover of these mRNAs in an sRNA-independent manner, providing one mechanism to release Hfq from the pre-bound mRNAs. Finally, our data indicate that sRNAs, once expressed, can either co-occupy Hfq with the mRNA or displace the mRNA from Hfq, suggesting mechanisms through which sRNAs rapidly access Hfq to induce sRNA-mediated gene regulation. Our data collectively demonstrate that Hfq dynamically changes its interactions with different RNAs in response to changes in cellular conditions.

scholarly journals Structural Insight Into the SARS-CoV-2 Nucleocapsid Protein C-Terminal Domain Reveals a Novel Recognition Mechanism for Viral Transcriptional Regulatory Sequences

2021 ◽  
Vol 8 ◽  
Author(s):  
Mei Yang ◽  
Suhua He ◽  
Xiaoxue Chen ◽  
Zhaoxia Huang ◽  
Ziliang Zhou ◽  
...  
Keyword(s):  
Nucleocapsid Protein ◽  
Protein C ◽  
Rna Binding ◽  
Regulatory Sequences ◽  
Recognition Mechanism ◽  
Stem Loop ◽  
Terminal Domain ◽  
Transcriptional Regulatory ◽  
Transcriptional Regulatory Mechanisms

Coronavirus disease 2019 (COVID-19) has caused massive disruptions to society and the economy, and the transcriptional regulatory mechanisms behind the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are poorly understood. Herein, we determined the crystal structure of the SARS-CoV-2 nucleocapsid protein C-terminal domain (CTD) at a resolution of 2.0 Å, and demonstrated that the CTD has a comparable distinct electrostatic potential surface to equivalent domains of other reported CoVs, suggesting that the CTD has novel roles in viral RNA binding and transcriptional regulation. Further in vitro biochemical assays demonstrated that the viral genomic intergenic transcriptional regulatory sequences (TRSs) interact with the SARS-CoV-2 nucleocapsid protein CTD with a flanking region. The unpaired adeno dinucleotide in the TRS stem-loop structure is a major determining factor for their interactions. Taken together, these results suggested that the nucleocapsid protein CTD is responsible for the discontinuous viral transcription mechanism by recognizing the different patterns of viral TRS during transcription.

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