scholarly journals Cys9, Cys104 and Cys207 of simian virus 40 Vp1 are essential for infectious virion formation in CV-1 cells

2001 ◽  
Vol 82 (8) ◽  
pp. 1935-1939 ◽  
Author(s):  
Editte Gharakhanian ◽  
Clare L. Fasching ◽  
Salvatore J. Orlando ◽  
Ana R. Perez
Keyword(s):  
Protein Interactions ◽  
Virus Assembly ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Protein Protein Interactions ◽  
Triple Mutant ◽  
Disulfide Linkage ◽  
Sv40 Infection ◽  
Virion Formation

Structural studies have implicated Cys9, Cys104 and Cys207 of simian virus 40 (SV40) Vp1 in disulfide bond formation. Recently, we have shown the three cysteines to be essential for disulfide linkage of Vp1 complexes in vitro. Here, the role of the three cysteines was explored during the course of SV40 infection. Single-, double- and triple-mutant Vp1 at Cys9, Cys104 and Cys207 continued to localize to the nuclei of transfected CV-1 cells and to bind DNA, but showed a range of abilities to form plaques. Only mutants containing the Cys9→Ser change showed defects in plaque formation. Single mutants at Cys9 formed small plaques; mutants at Cys9 . Cys104, Cys9 . Cys207 and Cys9 . Cys104 . Cys207 formed no plaques. All three isolated revertants contained back-mutations at the Vp1 Cys9 codon. These results further confirm the involvement of the three Vp1 cysteines in protein–protein interactions during virus assembly. Cys9 is critical for production of wild-type infectious virions, whereas Cys104 and Cys207 play secondary roles.

scholarly journals Roles of Disulfide Linkage and Calcium Ion-Mediated Interactions in Assembly and Disassembly of Virus-Like Particles Composed of Simian Virus 40 VP1 Capsid Protein

2001 ◽  
Vol 75 (1) ◽  
pp. 61-72 ◽  
Author(s):  
Ken-Ichiro Ishizu ◽  
Hajime Watanabe ◽  
Song-Iee Han ◽  
Shin-Nosuke Kanesashi ◽  
Mainul Hoque ◽  
...  
Keyword(s):  
Amino Acid ◽  
Calcium Ion ◽  
Insect Cells ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Ion Binding ◽  
Amino Acid Substitutions ◽  
Disulfide Linkage ◽  
Calcium Ion Binding

ABSTRACT The simian virus 40 capsid is composed of 72 pentamers of VP1 protein. Although the capsid is known to dissociate to pentamers in vitro following simultaneous treatment with reducing and chelating agents, the functional roles of disulfide linkage and calcium ion-mediated interactions are not clear. To elucidate the roles of these interactions, we introduced amino acid substitutions in VP1 at cysteine residues and at residues involved in calcium binding. We expressed the mutant proteins in a baculovirus system and analyzed both their assembly into virus-like particles (VLPs) in insect cells and the disassembly of those VLPs in vitro. We found that disulfide linkages at both Cys-9 and Cys-104 conferred resistance to proteinase K digestion on VLPs, although neither linkage was essential for the formation of VLPs in insect cells. In particular, reduction of the disulfide linkage at Cys-9 was found to be critical for VLP dissociation to VP1 pentamers in the absence of calcium ions, indicating that disulfide linkage at Cys-9 prevents VLP dissociation, probably by increasing the stability of calcium ion binding. We found that amino acid substitutions at carboxy-terminal calcium ion binding sites (Glu-329, Glu-330, and Asp-345) resulted in the frequent formation of unusual tubular particles as well as VLPs in insect cells, indicating that these residues affect the accuracy of capsid assembly. In addition, unexpectedly, amino acid substitutions at any of the calcium ion binding sites tested, especially at Glu-157, resulted in increased stability of VLPs in the absence of calcium ions in vitro. These results suggest that appropriate affinities of calcium ion binding are responsible for both assembly and disassembly of the capsid.

scholarly journals The Simian Virus 40 Core Origin Contains Two Separate Sequence Modules That Support T-Antigen Double-Hexamer Assembly

2000 ◽  
Vol 74 (18) ◽  
pp. 8589-8600 ◽  
Author(s):  
K. R. Sreekumar ◽  
Andrea E. Prack ◽  
Danielle R. Winters ◽  
Brett A. Barbaro ◽  
Peter A. Bullock
Keyword(s):  
Protein Interactions ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Protein Protein Interactions ◽  
Rich Region ◽  
Subsequent Formation ◽  
Sv40 Origin ◽  
Additional Protein ◽  
Assembly Unit

ABSTRACT Using subfragments of the simian virus 40 (SV40) core origin, we demonstrate that two alternative modules exist for the assembly of T-antigen (T-ag) double hexamers. Pentanucleotides 1 and 3 and the early palindrome (EP) constitute one assembly unit, while pentanucleotides 2 and 4 and the AT-rich region constitute a second, relatively weak, assembly unit. Related studies indicate that on the unit made up of pentanucleotide 1 and 3 and the EP assembly unit, the first hexamer forms on pentanucleotide 1 and that owing to additional protein-DNA and protein-protein interactions, the second hexamer is able to form on pentanucleotide 3. Oligomerization on the unit made up of pentanucleotide 2 and 4 and the AT-rich region is initiated by assembly of a hexamer on pentanucleotide 4; subsequent formation of the second hexamer takes place on pentanucleotide 2. Given that oligomerization on the SV40 origin is limited to double-hexamer formation, it is likely that only a single module is used for the initial assembly of T-ag double hexamers. Finally, we discuss the evidence that nucleotide hydrolysis is required for the remodeling events that result in the utilization of the second assembly unit.

scholarly journals Mutation Effects on Remote Epitopes of An Autoantigen Decoded with Simulated B-Factors

2019 ◽  
Author(s):  
Yuan-Ping Pang ◽  
Marta Casal Moura ◽  
Gwen E. Thompson ◽  
Amber M. Hummel ◽  
Darlene R. Nelson ◽  
...  
Keyword(s):  
Autoimmune Diseases ◽  
Protein Interactions ◽  
Granulomatosis With Polyangiitis ◽  
Wild Type ◽  
Protein Protein Interactions ◽  
Triple Mutant ◽  
Experimental Conditions ◽  
Chain Flexibility

Proteinase 3 (PR3) is a neutrophil serine protease targeted by anti-neutrophil cytoplasmic antibodies (ANCAs) in the autoimmune disease granulomatosis with polyangiitis (GPA)1–5. PR3 mutants were developed to investigate how PR3 interacts with the ANCAs and whether the interactions can be intervened by therapeutics. One mutant with a Ser195Ala mutation (iPR3-Val103) recognized as many ANCAs as wild-type PR3 (PR3-Val103)6–9, indicating that PR3-Val103 and iPR3-Val103 have equivalent ANCA-binding capabilities. A triple mutant of the latter (iHm5-Val103) bound a monoclonal antibody (moANCA518) from a patient with GPA on an epitope remote from the mutation sites. Unexpectedly, the corresponding epitope of iPR3-Val103 was inaccessible to moANCA518 under the same experimental conditions10,11. These observations demonstrate that a latent epitope of PR3 can be activated surprisingly by remote mutations in PR311. Here we report a comparative analysis of simulated B-factors (i.e., measurements of local mobility) of PR3-Val103, iPR3-Val103, and iHm5-Val103, demonstrating that the binding of moANCA518 to iHm5-Val103 is enabled by an increase in main-chain flexibility in the latent epitope caused by the remote muta-tions in iHm5-Val103. This epitope activation—achieved in vitro by remote mutations as we demonstrated or in vivo conceivably by remote protein»protein interactions12 or remote po-lymorphisms—may be a fundamental feature of antibody-mediated autoimmune diseases. Rigidifying B-cell epitopes on an autoantigen with therapeutics designed using the B-factor analysis disclosed here may lead to effective treatments for these autoimmune diseases by making the autoantigen inaccessible to existing autoantibodies. This analysis may also be used to predict and characterize epitopes and remote mutation effects.

scholarly journals Transcriptional activation by the parvoviral nonstructural protein NS-1 is mediated via a direct interaction with Sp1.

1995 ◽  
Vol 15 (1) ◽  
pp. 524-533 ◽  
Author(s):  
J K Krady ◽  
D C Ward
Keyword(s):  
Protein Interactions ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Nonstructural Protein ◽  
Direct Interaction ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Viral Gene

The nonstructural protein NS-1, encoded by the parvovirus minute virus of mice, is a potent regulator of viral gene expression. NS-1 does not bind DNA in a sequence-specific manner, and the mechanism by which it modulates viral promoter function is unclear. We have used Gal4-NS-1 fusion protein constructs to identify and characterize an activating domain encoded within the C-terminal 88 amino acids of NS-1 which competes effectively with the acidic activator domain of the herpes simplex virus VP16 protein. DNA affinity chromatography and immunoprecipitation experiments demonstrate that protein-protein interactions between the transcription factor Sp1 and NS-1 are required to bind NS-1 to promoter DNA in vitro. Cotransfection of Gal4-NS-1 and Sp1-VP16 acidic activator constructs into Drosophila melanogaster Schneider cells, which lack endogenous Sp1, stimulates transcription from a minimal promoter containing five Gal4 binding sites, while single-construct transfections do not. Cotransfection of Schneider cells with wild-type NS-1 and Sp1 constructs activates transcription from a simian virus 40 promoter 10- to 30-fold over that of either construct alone. Thus, Sp1-NS-1 interactions in vivo can stimulate transcription from a heterologous promoter containing Sp1 binding sites.

scholarly journals Importance of Vp1 Calcium-Binding Residues in Assembly, Cell Entry, and Nuclear Entry of Simian Virus 40

2003 ◽  
Vol 77 (13) ◽  
pp. 7527-7538 ◽  
Author(s):  
Peggy P. Li ◽  
Akira Naknanishi ◽  
Mary A. Tran ◽  
Ken-Ichiro Ishizu ◽  
Masaaki Kawano ◽  
...  
Keyword(s):  
Calcium Ions ◽  
Calcium Binding ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Cell Entry ◽  
Nuclear Entry ◽  
Virion Assembly ◽  
Sv40 Infection ◽  
Infection Processes ◽  
Virion Formation

ABSTRACT For polyomaviruses, calcium ions are known to be essential for virion integrity and for the assembly of capsid structures. To define the role of calcium ions in the life cycle of the virus, we analyzed simian virus 40 (SV40) mutants in which structurally deduced calcium-binding amino acids of Vp1 were mutated singly and in combination. Our study provides evidence that calcium ions mediate not only virion assembly but also the initial infection processes of cell entry and nuclear entry. Mutations at Glu48, Glu157, Glu160, Glu216, and/or Glu330 are correlated with different extents of packaging defects. The low packaging ability of mutant E216R suggests the need to position the Glu216 side chain for proper virion formation. All other mutants selected for further analysis produced virus-like particles (VLPs) but were poorly infectious. The VLPs of mutant E330K could not attach to or enter the cell, and mutant E157A-E160A and E216K VLPs entered the cell but failed to enter the nucleus, apparently as a result of premature VLP dissociation. Our results show that five of the seven acidic side chains at the two calcium-binding sites—Glu48 and Glu330 (site 1), Glu157 and Glu160 (site 2), and Glu216 (both sites)—are important for SV40 infection. We propose that calcium coordination imparts not only stability but also structural flexibility to the virion, allowing the acquisition or loss of the ion at the two sites to control virion formation in the nucleus, as well as virion structural alterations at the cell surface and in the cytoplasm early during infection.

scholarly journals Protein-Protein Interactions of the Primase Subunits p58 and p48 with Simian Virus 40 T Antigen Are Required for Efficient Primer Synthesis in a Cell-free System

2000 ◽  
Vol 275 (23) ◽  
pp. 17328-17337 ◽  
Author(s):  
Klaus Weisshart ◽  
Hella Förster ◽  
Elisabeth Kremmer ◽  
Bernhard Schlott ◽  
Frank Grosse ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
Protein Protein Interactions ◽  
Free System ◽  
Cell Free System ◽  
A Cell

scholarly journals Cys9, Cys104 and Cys207 of simian virus 40 Vp1 are essential for inter-pentamer disulfide-linkage and stabilization in cell-free lysates

1999 ◽  
Vol 80 (9) ◽  
pp. 2481-2489 ◽  
Author(s):  
Christine C. Jao ◽  
Mary K. Weidman ◽  
Ana R. Perez ◽  
Editte Gharakhanian
Keyword(s):  
Disulfide Bonds ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Wild Type ◽  
Triple Mutant ◽  
Disulfide Linkage ◽  
Sds Page ◽  
Reticulocyte Lysates ◽  
Disulfide Interactions ◽  
Serine Codons

Previous studies have implicated disulfide bonds between Vp1 molecules in the stabilization of the simian virus 40 (SV40) capsid. To identify the cysteine residues involved in intermolecular disulfide interactions, systematic oligo-directed mutagenesis of cysteine codons to serine codons was initiated. Wild-type and mutant Vp1 proteins were produced in rabbit reticulocyte lysates and were allowed to interact post-translationally. Disulfide-linked Vp1 complexes were assessed via non-reducing SDS–PAGE and via sucrose-gradient sedimentation. Wild-type Vp1 forms 7S pentamers followed by 12S disulfide-linked multi-pentameric complexes in cell-free lysates. Mutagenesis of all seven cysteine codons abolished Vp1 12S complexes, but did not affect pentamer formation. A quadruple Vp1 mutant at Cys49, Cys87, Cys254 and Cys267 continued to form 12S complexes, whereas the major products of the Cys9, Cys104 and Cys207 triple mutant Vp1 were 7S pentamers. Single and double mutant Vp1 proteins at the three cysteines affected continued to form 12S complexes, but to a lesser extent. Thus, inter-pentamer disulfide bonds at Cys9, Cys104 and Cys207 are essential and sufficient for stabilization of Vp1 complexes in cell-free lysates. These results are in agreement with previous structural studies of SV40 that implicated the same three residues in disulfide linkage in the capsid. Possible parameters for the involvement of the three cysteines are discussed.

Probing the 14-3-3 Isoform-Specificity Profile of Interactions Stabilized by Fusicoccin A

2020 ◽  
Author(s):  
James Frederich ◽  
Ananya Sengupta ◽  
Josue Liriano ◽  
Ewa A. Bienkiewicz ◽  
Brian G. Miller
Keyword(s):  
Protein Interactions ◽  
Neurological Diseases ◽  
Adapter Proteins ◽  
Protein Protein Interactions ◽  
Specific Expression ◽  
Individual Client ◽  
Isoform Specificity ◽  
Fusicoccin A

Fusicoccin A (FC) is a fungal phytotoxin that stabilizes protein–protein interactions (PPIs) between 14-3-3 adapter proteins and their phosphoprotein interaction partners. In recent years, FC has emerged as an important chemical probe of human 14-3-3 PPIs implicated in cancer and neurological diseases. These previous studies have established the structural requirements for FC-induced stabilization of 14-3-3·client phosphoprotein complexes; however, the effect of different 14-3-3 isoforms on FC activity has not been systematically explored. This is a relevant question for the continued development of FC variants because there are seven distinct isoforms of 14-3-3 in humans. Despite their remarkable sequence and structural similarities, a growing body of experimental evidence supports both tissue-specific expression of 14-3-3 isoforms and isoform-specific functions <i>in vivo</i>. Herein, we report the isoform-specificity profile of FC <i>in vitro</i>using recombinant human 14-3-3 isoforms and a focused library of fluorescein-labeled hexaphosphopeptides mimicking the C-terminal 14-3-3 recognition domains of client phosphoproteins targeted by FC in cell culture. Our results reveal modest isoform preferences for individual client phospholigands and demonstrate that FC differentially stabilizes PPIs involving 14-3-3s. Together, these data provide strong motivation for the development of non-natural FC variants with enhanced selectivity for individual 14-3-3 isoforms.

scholarly journals Identification and Biochemical Characterization of High Mobility Group Protein 20A as a Novel Ca2+/S100A6 Target

Biomolecules ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 510
Author(s):  
Maho Yamamoto ◽  
Rina Kondo ◽  
Haruka Hozumi ◽  
Seita Doi ◽  
Miwako Denda ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Biochemical Characterization ◽  
S100 Protein ◽  
High Mobility ◽  
Dependent Manner ◽  
Protein Signaling ◽  
Protein Protein Interactions ◽  
High Mobility Group Protein ◽  
Pulldown Assay

During screening of protein-protein interactions, using human protein arrays carrying 19,676 recombinant glutathione s-transferase (GST)-fused human proteins, we identified the high-mobility protein group 20A (HMG20A) as a novel S100A6 binding partner. We confirmed the Ca2+-dependent interaction of HMG20A with S100A6 by the protein array method, biotinylated S100A6 overlay, and GST-pulldown assay in vitro and in transfected COS-7 cells. Co-immunoprecipitation of S100A6 with HMG20A from HeLa cells in a Ca2+-dependent manner revealed the physiological relevance of the S100A6/HMG20A interaction. In addition, HMG20A has the ability to interact with S100A1, S100A2, and S100B in a Ca2+-dependent manner, but not with S100A4, A11, A12, and calmodulin. S100A6 binding experiments using various HMG20A mutants revealed that Ca2+/S100A6 interacts with the C-terminal region (residues 311–342) of HMG20A with stoichiometric binding (HMG20A:S100A6 dimer = 1:1). This was confirmed by the fact that a GST-HMG20A mutant lacking the S100A6 binding region (residues 311–347, HMG20A-ΔC) failed to interact with endogenous S100A6 in transfected COS-7 cells, unlike wild-type HMG20A. Taken together, these results identify, for the first time, HMG20A as a target of Ca2+/S100 proteins, and may suggest a novel linkage between Ca2+/S100 protein signaling and HMG20A function, including in the regulation of neural differentiation.

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