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Lin HS, Li CH, Chen LW, Wang SS, Chen LY, Hung CH, Lin CL, Chang PJ. The varicella-zoster virus ORF16 protein promotes both the nuclear transport and the protein abundance of the viral DNA polymerase subunit ORF28. Virus Res 2024; 345:199379. [PMID: 38643859 PMCID: PMC11061344 DOI: 10.1016/j.virusres.2024.199379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 04/19/2024] [Accepted: 04/19/2024] [Indexed: 04/23/2024]
Abstract
Although all herpesviruses utilize a highly conserved replication machinery to amplify their viral genomes, different members may have unique strategies to modulate the assembly of their replication components. Herein, we characterize the subcellular localization of seven essential replication proteins of varicella-zoster virus (VZV) and show that several viral replication enzymes such as the DNA polymerase subunit ORF28, when expressed alone, are localized in the cytoplasm. The nuclear import of ORF28 can be mediated by the viral DNA polymerase processivity factor ORF16. Besides, ORF16 could markedly enhance the protein abundance of ORF28. Noteworthily, an ORF16 mutant that is defective in nuclear transport still retained the ability to enhance ORF28 abundance. The low abundance of ORF28 in transfected cells was due to its rapid degradation mediated by the ubiquitin-proteasome system. We additionally reveal that radicicol, an inhibitor of the chaperone Hsp90, could disrupt the interaction between ORF16 and ORF28, thereby affecting the nuclear entry and protein abundance of ORF28. Collectively, our findings imply that the cytoplasmic retention and rapid degradation of ORF28 may be a key regulatory mechanism for VZV to prevent untimely viral DNA replication, and suggest that Hsp90 is required for the interaction between ORF16 and ORF28.
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Affiliation(s)
- Huang-Shen Lin
- Department of Internal Medicine, Division of Infectious Diseases, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan; Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Cheng-Han Li
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Lee-Wen Chen
- Department of Respiratory Care, Chang Gung University of Science and Technology, Chiayi 61363, Taiwan; Department of Pediatric Surgery, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan
| | - Shie-Shan Wang
- Department of Pediatric Surgery, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan; School of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Li-Yu Chen
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Chien-Hui Hung
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Chun-Liang Lin
- Department of Nephrology, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan
| | - Pey-Jium Chang
- Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan; Department of Nephrology, Chang Gung Memorial Hospital, Chiayi 61363, Taiwan.
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2
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Döhner K, Serrero MC, Sodeik B. The role of nuclear pores and importins for herpes simplex virus infection. Curr Opin Virol 2023; 62:101361. [PMID: 37672874 DOI: 10.1016/j.coviro.2023.101361] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 07/31/2023] [Accepted: 08/08/2023] [Indexed: 09/08/2023]
Abstract
Microtubule transport and nuclear import are functionally connected, and the nuclear pore complex (NPC) can interact with microtubule motors. For several alphaherpesvirus proteins, nuclear localization signals (NLSs) and their interactions with specific importin-α proteins have been characterized. Here, we review recent insights on the roles of microtubule motors, capsid-associated NLSs, and importin-α proteins for capsid transport, capsid docking to NPCs, and genome release into the nucleoplasm, as well as the role of importins for nuclear viral transcription, replication, capsid assembly, genome packaging, and nuclear capsid egress. Moreover, importin-α proteins exert antiviral effects by promoting the nuclear import of transcription factors inducing the expression of interferons (IFN), cytokines, and IFN-stimulated genes, and the IFN-inducible MxB restricts capsid docking to NPCs.
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Affiliation(s)
- Katinka Döhner
- Institute of Virology, Hannover Medical School, Hannover, Germany; Department of Dermatology and Allergy, Hannover Medical School, Hannover, Germany; RESIST - Cluster of Excellence, Hannover Medical School, Hannover, Germany.
| | - Manutea C Serrero
- Institute of Virology, Hannover Medical School, Hannover, Germany; RESIST - Cluster of Excellence, Hannover Medical School, Hannover, Germany
| | - Beate Sodeik
- Institute of Virology, Hannover Medical School, Hannover, Germany; RESIST - Cluster of Excellence, Hannover Medical School, Hannover, Germany; DZIF - German Centre for Infection Research, Braunschweig, Hannover, Germany.
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Characterization of an In Vivo Z-DNA Detection Probe Based on a Cell Nucleus Accumulating Intrabody. Mol Biotechnol 2017; 58:585-94. [PMID: 27351554 DOI: 10.1007/s12033-016-9958-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Left-handed Z-DNA is a physiologically unstable DNA conformation, and its existence in vivo can be attributed to localized torsional distress. Despite evidence for the existence of Z-DNA in vivo, its precise role in the control of gene expression is not fully understood. Here, an in vivo probe based on an anti-Z-DNA intrabody is proposed for native Z-DNA detection. The probe was used for chromatin immunoprecipitation of potential Z-DNA-forming sequences in the human genome. One of the isolated putative Z-DNA-forming sequences was cloned upstream of a reporter gene expression cassette under control of the CMV promoter. The reporter gene encoded an antibody fragment fused to GFP. Transient co-transfection of this vector along with the Z-probe coding vector improved reporter gene expression. This improvement was demonstrated by measuring reporter gene mRNA and protein levels and the amount of fluorescence in co-transfected CHO-K1 cells. These results suggest that the presence of the anti-Z-DNA intrabody can interfere with a Z-DNA-containing reporter gene expression. Therefore, this in vivo probe for the detection of Z-DNA could be used for global correlation of Z-DNA-forming sequences and gene expression regulation.
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Marshall KS, Cohen MJ, Fonseca GJ, Todorovic B, King CR, Yousef AF, Zhang Z, Mymryk JS. Identification and characterization of multiple conserved nuclear localization signals within adenovirus E1A. Virology 2014; 454-455:206-14. [DOI: 10.1016/j.virol.2014.02.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 12/18/2013] [Accepted: 02/19/2014] [Indexed: 11/25/2022]
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Regulated transport into the nucleus of herpesviridae DNA replication core proteins. Viruses 2013; 5:2210-34. [PMID: 24064794 PMCID: PMC3798897 DOI: 10.3390/v5092210] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/03/2013] [Accepted: 09/04/2013] [Indexed: 12/11/2022] Open
Abstract
The Herpesvirdae family comprises several major human pathogens belonging to three distinct subfamilies. Their double stranded DNA genome is replicated in the nuclei of infected cells by a number of host and viral products. Among the latter the viral replication complex, whose activity is strictly required for viral replication, is composed of six different polypeptides, including a two-subunit DNA polymerase holoenzyme, a trimeric primase/helicase complex and a single stranded DNA binding protein. The study of herpesviral DNA replication machinery is extremely important, both because it provides an excellent model to understand processes related to eukaryotic DNA replication and it has important implications for the development of highly needed antiviral agents. Even though all known herpesviruses utilize very similar mechanisms for amplification of their genomes, the nuclear import of the replication complex components appears to be a heterogeneous and highly regulated process to ensure the correct spatiotemporal localization of each protein. The nuclear transport process of these enzymes is controlled by three mechanisms, typifying the main processes through which protein nuclear import is generally regulated in eukaryotic cells. These include cargo post-translational modification-based recognition by the intracellular transporters, piggy-back events allowing coordinated nuclear import of multimeric holoenzymes, and chaperone-assisted nuclear import of specific subunits. In this review we summarize these mechanisms and discuss potential implications for the development of antiviral compounds aimed at inhibiting the Herpesvirus life cycle by targeting nuclear import of the Herpesvirus DNA replicating enzymes.
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Takahashi T, Tamura M, Takasu T. Diagnostic value of a "wide-range" quantitative nested real-time PCR assay for varicella zoster virus myelitis. J Med Virol 2013; 85:2042-55. [PMID: 23934732 DOI: 10.1002/jmv.23690] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/04/2013] [Indexed: 12/29/2022]
Abstract
Myelitis is one of the rarest neurological complications of varicella zoster virus (VZV) infection. In this study, the authors remodeled the "wide-range" quantitative nested real-time (QNRT) polymerase chain reaction (PCR) assay to quantitatively detect a small amount of VZV-DNA in cerebrospinal fluid (CSF). For use as a specific internal control "calibrator," an original mutation-VZV (MZ) plasmid was developed. The initial copy number of VZV-DNA in CSF specimens was measured by the amplification rate of the MZ-plasmid. For 17 consecutive CSF specimens collected from three elderly patients with VZV myelitis, the diagnostic value of the wide-range QNRT-PCR assay was evaluated and compared with other conventional PCR assays and enzyme immunoassay (EIA). The MZ-plasmid demonstrated statistically uniform amplifications (F=1.016) against a wide range (1-100,000) of copy numbers of mimic VZV-DNA. The wide-range QNRT-PCR assay quantitatively and rapidly (within 48 hr) detected 5,863, 3,052, 958, and 6,721 copies/ml of VZV-DNA in the CSF specimens collected from all patients in the acute phase. Additionally, there was a significant difference (*P=0.023) in the copy number of VZV-DNA between before and after acyclovir treatment. Other conventional single PCR assays all revealed negative results, but were nevertheless time-consuming (7 days). The IgG EIA-value for VZV was continually elevated throughout the clinical course of all patients. The MZ-plasmid was thus regarded as an appropriate "calibrator" in the wide-range QNRT-PCR assay. This assay is a novel, rapid, accurate, quantitative, and highly sensitive technique, and will contribute as a reliable and useful clinical examination for the rapid diagnosis of VZV infection to central nervous system.
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Kim S, Ahn BC, O'Callaghan DJ, Kim SK. The early UL31 gene of equine herpesvirus 1 encodes a single-stranded DNA-binding protein that has a nuclear localization signal sequence at the C-terminus. Virology 2012; 432:306-15. [PMID: 22721961 DOI: 10.1016/j.virol.2012.05.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 05/15/2012] [Accepted: 05/24/2012] [Indexed: 11/26/2022]
Abstract
The amino acid sequence of the UL31 protein (UL31P) of equine herpesvirus 1 (EHV-1) has homology to that of the ICP8 of herpes simplex virus type 1 (HSV-1). Here we show that the UL31 gene is synergistically trans-activated by the IEP and the UL5P (EICP27). Detection of the UL31 RNA transcript and the UL31P in EHV-1-infected cells at 6h post-infection (hpi) as well as metabolic inhibition assays indicated that UL31 is an early gene. The UL31P preferentially bound to single-stranded DNA over double-stranded DNA in gel shift assays. Subcellular localization of the green fluorescent protein (GFP)-UL31 fusion proteins revealed that the C-terminal 32 amino acid residues of the UL31P are responsible for the nuclear localization. These findings may contribute to defining the role of the UL31P single-stranded DNA-binding protein in EHV-1 DNA replication.
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Affiliation(s)
- Seongman Kim
- Department of Microbiology and Immunology, Center for Molecular and Tumor Virology, Louisiana State University Health Sciences Center, Shreveport, LA 71130-3932, USA
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Zhang Z, Selariu A, Warden C, Huang G, Huang Y, Zaccheus O, Cheng T, Xia N, Zhu H. Genome-wide mutagenesis reveals that ORF7 is a novel VZV skin-tropic factor. PLoS Pathog 2010; 6:e1000971. [PMID: 20617166 PMCID: PMC2895648 DOI: 10.1371/journal.ppat.1000971] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Accepted: 05/27/2010] [Indexed: 11/30/2022] Open
Abstract
The Varicella Zoster Virus (VZV) is a ubiquitous human alpha-herpesvirus that is the causative agent of chicken pox and shingles. Although an attenuated VZV vaccine (v-Oka) has been widely used in children in the United States, chicken pox outbreaks are still seen, and the shingles vaccine only reduces the risk of shingles by 50%. Therefore, VZV still remains an important public health concern. Knowledge of VZV replication and pathogenesis remains limited due to its highly cell-associated nature in cultured cells, the difficulty of generating recombinant viruses, and VZV's almost exclusive tropism for human cells and tissues. In order to circumvent these hurdles, we cloned the entire VZV (p-Oka) genome into a bacterial artificial chromosome that included a dual-reporter system (GFP and luciferase reporter genes). We used PCR-based mutagenesis and the homologous recombination system in the E. coli to individually delete each of the genome's 70 unique ORFs. The collection of viral mutants obtained was systematically examined both in MeWo cells and in cultured human fetal skin organ samples. We use our genome-wide deletion library to provide novel functional annotations to 51% of the VZV proteome. We found 44 out of 70 VZV ORFs to be essential for viral replication. Among the 26 non-essential ORF deletion mutants, eight have discernable growth defects in MeWo. Interestingly, four ORFs were found to be required for viral replication in skin organ cultures, but not in MeWo cells, suggesting their potential roles as skin tropism factors. One of the genes (ORF7) has never been described as a skin tropic factor. The global profiling of the VZV genome gives further insights into the replication and pathogenesis of this virus, which can lead to improved prevention and therapy of chicken pox and shingles. The Varicella Zoster Virus (VZV) is the causative agent of chicken pox and shingles. The long-term efficacy of the current chickenpox vaccine is yet to be determined, and the current shingles vaccine fails to provide protective immunity for a substantial number of individuals. Shingles can also lead to post-herpetic neuralgia (PHN), a debilitating condition associated with an intractable pain that can linger for life. Therefore, VZV remains an important public health concern. We use growth-rate analysis of our genome-wide deletion library to determine the essentiality of all known VZV genes, including novel annotations for 51% of the VZV proteome. We also discovered a novel skin-tropic factor encoded by ORF7. Overall, our identification of genes essential for VZV replication and pathogenesis will serve as the basis for multiple in-depth genetic studies of VZV, which can lead to improved prevention and therapy of chicken pox and shingles. For example, essential genes may be appealing drug targets and genes whose deletion causes a substantial growth defect may be prospective candidates for novel live attenuated vaccines.
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Affiliation(s)
- Zhen Zhang
- Department of Microbiology and Molecular Genetics, UMNDJ-Newark, Newark, New Jersey, United States of America
| | - Anca Selariu
- Department of Microbiology and Molecular Genetics, UMNDJ-Newark, Newark, New Jersey, United States of America
| | - Charles Warden
- Department of Microbiology and Molecular Genetics, UMNDJ-Newark, Newark, New Jersey, United States of America
| | - Grace Huang
- Department of Microbiology and Molecular Genetics, UMNDJ-Newark, Newark, New Jersey, United States of America
| | - Ying Huang
- Department of Microbiology and Molecular Genetics, UMNDJ-Newark, Newark, New Jersey, United States of America
| | - Oluleke Zaccheus
- Department of Microbiology and Molecular Genetics, UMNDJ-Newark, Newark, New Jersey, United States of America
| | - Tong Cheng
- National Institute of Diagnostics and Vaccine Development in Infectious Diseases, Xiamen University, Xiamen, China
| | - Ningshao Xia
- National Institute of Diagnostics and Vaccine Development in Infectious Diseases, Xiamen University, Xiamen, China
| | - Hua Zhu
- Department of Microbiology and Molecular Genetics, UMNDJ-Newark, Newark, New Jersey, United States of America
- * E-mail:
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Au V, Yu M, Carstens EB. Characterization of a baculovirus nuclear localization signal domain in the late expression factor 3 protein. Virology 2009; 385:209-17. [DOI: 10.1016/j.virol.2008.10.051] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Revised: 10/12/2008] [Accepted: 10/30/2008] [Indexed: 10/21/2022]
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10
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Kyratsous CA, Silverstein SJ. BAG3, a host cochaperone, facilitates varicella-zoster virus replication. J Virol 2007; 81:7491-503. [PMID: 17475647 PMCID: PMC1933350 DOI: 10.1128/jvi.00442-07] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2007] [Accepted: 04/25/2007] [Indexed: 12/29/2022] Open
Abstract
Varicella-zoster virus (VZV) establishes a lifelong latent infection in the dorsal root ganglia of the host. During latency, a subset of virus-encoded regulatory proteins is detected; however, they are excluded from the nucleus. ORF29p, a single-stranded DNA binding protein, is one of these latency-associated proteins. We searched for cell proteins that interact with ORF29p and identified BAG3. BAG3, Hsp70/Hsc70, and Hsp90 colocalize with ORF29p in nuclear transcription/replication factories during lytic replication of VZV. Pharmacological intercession of Hsp90 activity with ansamycin antibiotics or depletion of BAG3 by small interfering RNA results in inhibition of virus replication. Replication in BAG3-depleted cell lines is restored by complementation with exogenous BAG3. Alteration of host chaperone activity provides a novel means of regulating virus replication.
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Affiliation(s)
- Christos A Kyratsous
- Department of Microbiology, College of Physicians and Surgeons, Columbia University, 701 W. 168th St., New York, NY 10032, USA
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Cohen JI, Krogmann T, Pesnicak L, Ali MA. Absence or overexpression of the Varicella-Zoster Virus (VZV) ORF29 latency-associated protein impairs late gene expression and reduces VZV latency in a rodent model. J Virol 2006; 81:1586-91. [PMID: 17151102 PMCID: PMC1797561 DOI: 10.1128/jvi.01220-06] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Varicella-zoster virus (VZV) ORF29 encodes the viral single-stranded DNA binding protein and is expressed during latency in human ganglia. We constructed an ORF29 deletion mutant virus and showed that the virus could replicate only in cells expressing ORF29. An ORF29-repaired virus, in which ORF29 was driven by a cytomegalovirus promoter, grew to peak titers similar to those seen with the parental virus. The level of ORF29 protein in cells infected with the repaired virus was greater than that seen with parental virus. Infection of cells with either the ORF29 deletion or repaired virus resulted in similar levels of VZV immediate-early proteins but reduced levels of glycoprotein E compared to those observed with parental virus. Cotton rats infected with the ORF29 deletion mutant had a markedly reduced frequency of latent infection in dorsal root ganglia compared with those infected with parental virus (P < 0.00001). In contrast, infection of animals with the ORF29 deletion mutant resulted in a frequency of ganglionic infection at 3 days similar to that seen with the parental virus. Animals infected with the ORF29-repaired virus, which overexpresses ORF29, also had a reduced frequency of latent infection compared with those infected with parental virus (P = 0.0044). These studies indicate that regulation of ORF29 at appropriate levels is critical for VZV latency in a rodent model.
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Affiliation(s)
- Jeffrey I Cohen
- Laboratory of Clinical Infectious Diseases, Bldg. 10, Room 11N234, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA.
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Stallings CL, Silverstein SJ. Posttranslational modification and cell type-specific degradation of varicella-zoster virus ORF29p. J Virol 2006; 80:10836-46. [PMID: 16956951 PMCID: PMC1641786 DOI: 10.1128/jvi.00966-06] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ORF29 gene of varicella-zoster virus encodes a single-stranded DNA binding protein that is predominantly nuclear during lytic infection but appears to be restricted to the cytoplasm of latently infected neurons. Following reactivation, ORF29p accumulates in the nuclei of neurons, suggesting that its confinement to the cytosol may be critical for maintaining quiescence. When autonomously expressed, ORF29p accumulates in the nuclei of fibroblasts and the cytoplasm of cells (guinea pig enteric neurons) and cell lines (U373MG) of neuronal origin. Inhibition of the 26S proteasome redirects the accumulation of ORF29p to the nucleus in cells of neuronal origin. Here, we show that ORF29p is ubiquitinated and sumoylated in 293T cells and subsequently degraded from the N terminus. Ubiquitinated ORF29p accumulates in both the nuclei and the cytoplasm of fibroblasts, but degradation products are seen primarily in the cytoplasm. Modification and degradation of ORF29p occurs in 293T, U373MG, and MeWo cells. Therefore, these processes are ubiquitous; however, the robustness of the degradation process is cell type specific. The proteasome-mediated mechanism of nuclear exclusion in U373MG cells is an active process that is not specific for the endogenous ORF29p nuclear localization signal but can be saturated by protein stabilization or overexpression, which leads to nuclear accumulation of ORF29p. The evidence for ORF29p ubiquitination and previous data regarding the effect of proteasome inhibitors on the abundance and distribution of ORF29p implicate the 26S proteasome in influencing the protein's cell type-specific localization.
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Stallings CL, Duigou GJ, Gershon AA, Gershon MD, Silverstein SJ. The cellular localization pattern of Varicella-Zoster virus ORF29p is influenced by proteasome-mediated degradation. J Virol 2006; 80:1497-512. [PMID: 16415026 PMCID: PMC1346923 DOI: 10.1128/jvi.80.3.1497-1512.2006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Varicella-zoster virus (VZV) open reading frame 29 (ORF29) encodes a single-stranded DNA binding protein. During lytic infection, ORF29p is localized primarily to infected-cell nuclei, whereas during latency it appears in the cytoplasm of infected neurons. Following reactivation, ORF29p accumulates in the nucleus. In this report, we analyze the cellular localization patterns of ORF29p during VZV infection and during autonomous expression. Our results demonstrate that ORF29p is excluded from the nucleus in a cell-type-specific manner and that its cellular localization pattern may be altered by subsequent expression of VZV ORF61p or herpes simplex virus type 1 ICP0. In these cases, ORF61p and ICP0 induce nuclear accumulation of ORF29p in cell lines where it normally remains cytoplasmic. One cellular system utilized by ICP0 to influence protein abundance is the proteasome degradation pathway. Inhibition of the 26S proteasome, but not heat shock treatment, resulted in accumulation of ORF29p in the nucleus, similar to the effect of ICP0 expression. Immunofluorescence microscopy and pulse-chase experiments reveal that stabilization of ORF29p correlates with its nuclear accumulation and is dependent on a functional nuclear localization signal. ORF29p nuclear translocation in cultured enteric neurons and cells derived from an astrocytoma is reversible, as the protein's distribution and stability revert to the previous states when the proteasomal activity is restored. Thus, stabilization of ORF29p leads to its nuclear accumulation. Although proteasome inhibition induces ORF29p nuclear accumulation, this is not sufficient to reactivate latent VZV or target the immediate-early protein ORF62p to the nucleus in cultured guinea pig enteric neurons.
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MESH Headings
- Amino Acid Sequence
- Animals
- Cell Line
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Enteric Nervous System/metabolism
- Enteric Nervous System/virology
- Exons
- Guinea Pigs
- Herpesvirus 1, Human/genetics
- Herpesvirus 1, Human/metabolism
- Herpesvirus 3, Human/genetics
- Herpesvirus 3, Human/metabolism
- Herpesvirus 3, Human/pathogenicity
- Humans
- Immediate-Early Proteins/genetics
- Immediate-Early Proteins/metabolism
- Leupeptins/pharmacology
- Molecular Sequence Data
- Mutagenesis, Insertional
- Mutation
- Open Reading Frames
- Protease Inhibitors/pharmacology
- Proteasome Endopeptidase Complex/metabolism
- Proteasome Inhibitors
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Subcellular Fractions/metabolism
- Subcellular Fractions/virology
- Tissue Culture Techniques
- Ubiquitin-Protein Ligases/genetics
- Ubiquitin-Protein Ligases/metabolism
- Viral Proteins/genetics
- Viral Proteins/metabolism
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Affiliation(s)
- Christina L Stallings
- Integrated Program in Cellular, Molecular and Biophysical Studies, and Department of Microbiology, Columbia University College of Physicians and Surgeons, 701 W. 168th Street, New York, NY 10032, USA
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