Reactivation and lytic replication of EBV

Abstract Background Sterile alpha motif and HD domain 1 (SAMHD1) is a deoxynucleotide triphosphohydrolase (dNTPase) that restricts the infection of a variety of RNA and DNA viruses, including herpesviruses. The anti-viral function of SAMHD1 is associated with its dNTPase activity, which is regulated by several post-translational modifications, including phosphorylation, acetylation and ubiquitination. Our recent studies also demonstrated that the E3 SUMO ligase PIAS1 functions as an Epstein-Barr virus (EBV) restriction factor. However, whether SAMHD1 is regulated by PIAS1 to restrict EBV replication remains unknown. Results In this study, we showed that PIAS1 interacts with SAMHD1 and promotes its SUMOylation. We identified three lysine residues (K469, K595 and K622) located on the surface of SAMHD1 as the major SUMOylation sites. We demonstrated that phosphorylated SAMHD1 can be SUMOylated by PIAS1 and SUMOylated SAMHD1 can also be phosphorylated by viral protein kinases. We showed that SUMOylation-deficient SAMHD1 loses its anti-EBV activity. Furthermore, we demonstrated that SAMHD1 is associated with EBV genome in a PIAS1-dependent manner. Conclusion Our study reveals that PIAS1 synergizes with SAMHD1 to inhibit EBV lytic replication through protein–protein interaction and SUMOylation.

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A Replication-Defective Gammaherpesvirus Efficiently Establishes Long-Term Latency in Macrophages but Not in B Cells In Vivo

Journal of Virology ◽

10.1128/jvi.00186-08 ◽

2008 ◽

Vol 82 (17) ◽

pp. 8500-8508 ◽

Cited By ~ 17

Author(s):

Haiyan Li ◽

Kazufumi Ikuta ◽

John W. Sixbey ◽

Scott A. Tibbetts

Keyword(s):

B Cells ◽

Viral Genome ◽

Lytic Replication ◽

Mutant Virus ◽

Wild Type Virus ◽

Type Virus ◽

Wild Type ◽

Virus Latency

ABSTRACT Murine gammaherpesvirus 68 (γHV68 or MHV68) is genetically related to the human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), providing a useful system for in vivo studies of the virus-host relationship. To begin to address fundamental questions about the mechanisms of the establishment of gammaherpesvirus latency, we previously generated a replication-defective γHV68 lacking the expression of the single-stranded DNA binding protein encoded by orf6. In work presented here, we demonstrate that this mutant virus established a long-term infection in vivo that was molecularly identical to wild-type virus latency. Thus, despite the absence of an acute phase of lytic replication, the mutant virus established a chronic infection in which the viral genome (i) was maintained as an episome and (ii) expressed latency-associated, but not lytic replication-associated, genes. Macrophages purified from mice infected with the replication-defective virus harbored viral genome at a frequency that was nearly identical to that of wild-type γHV68; however, the frequency of B cells harboring viral genome was greatly reduced in the absence of lytic replication. Thus, this replication-defective gammaherpesvirus efficiently established in vivo infection in macrophages that was molecularly indistinguishable from wild-type virus latency. These data point to a critical role for lytic replication or reactivation in the establishment or maintenance of latent infection in B cells.

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A Kaposi's Sarcoma-Associated Herpesvirus Protein That Forms Inhibitory Complexes with Type I Interferon Receptor Subunits, Jak and STAT Proteins, and Blocks Interferon-Mediated Signal Transduction

Journal of Virology ◽

10.1128/jvi.02516-08 ◽

2009 ◽

Vol 83 (10) ◽

pp. 5056-5066 ◽

Cited By ~ 42

Author(s):

Sabine A. Bisson ◽

Anne-Laure Page ◽

Don Ganem

Keyword(s):

Kaposi's Sarcoma ◽

Human Tumor ◽

Kaposi’S Sarcoma ◽

Lytic Replication ◽

Type I Interferons ◽

Type I ◽

Type I Ifn ◽

Reading Frame ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Type I interferons (IFNs) are important mediators of innate antiviral defense and function by activating a signaling pathway through their cognate type I receptor (IFNAR). Here we report that lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) efficiently blocks type I IFN signaling and that an important effector of this blockade is the viral protein RIF, the product of open reading frame 10. RIF blocks IFN signaling by formation of inhibitory complexes that contain IFNAR subunits, the Janus kinases Jak1 and Tyk2, and the STAT2 transcription factor. Activation of both Tyk2 and Jak1 is inhibited, and abnormal recruitment of STAT2 to IFNAR1 occurs despite the decrement in Tyk2 activity. As a result of these actions, phosphorylation of both STAT2 and STAT1 is impaired, with subsequent failure of ISGF3 accumulation in the nucleus. The presence in the viral genome of potent inhibitors of type I IFN signaling, along with several viral genes that block IFN induction, highlights the importance of the IFN pathway in the control of this human tumor virus infection.

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Kaposi's Sarcoma-Associated Herpesvirus ori-Lyt-Dependent DNA Replication: DualRole of Replication and Transcription Activator

Journal of Virology ◽

10.1128/jvi.00990-06 ◽

2006 ◽

Vol 80 (24) ◽

pp. 12171-12186 ◽

Cited By ~ 51

Author(s):

Yan Wang ◽

Qiyi Tang ◽

Gerd G. Maul ◽

Yan Yuan

Keyword(s):

Dna Replication ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Lytic Replication ◽

Transcription Activator ◽

Binding Motifs ◽

Viral Propagation ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus ◽

Lytic Dna Replication

ABSTRACT Lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) is essential for viral propagation and pathogenicity. In Kaposi's sarcoma lesions, constant lytic replication plays a role in sustaining the population of latently infected cells that otherwise are quickly lost by segregation of latent viral episomes as spindle cells divide. Lytic DNA replication initiates from an origin (ori-Lyt) and requires trans-acting elements. Two functional ori-Lyts have been identified in the KSHV genome. Some cis-acting and trans-acting elements for ori-Lyt-dependent DNA replication have been found. Among these, K8 binding sites, a cluster of C/EBP binding motifs, and a replication and transcription activator (RTA) responsive element (RRE) are crucial cis-acting elements. Binding of K8 and RTA proteins to these motifs in ori-Lyt DNA was demonstrated to be absolutely essential for DNA replication. In the present study, functional roles of RTA in ori-Lyt-dependent DNA replication have been investigated. Two distinct functions of RTA were revealed. First, RTA activates an ori-Lyt promoter and initiates transcription across GC-rich tandem repeats. This RTA-mediated transcription is indispensable for DNA replication. Second, RTA is a component of the replication compartment, where RTA interacts with prereplication complexes composed of at least six core machinery proteins and K8. The prereplication complexes are recruited to ori-Lyt DNA through RTA, which interacts with the RRE, as well as K8, which binds to a cluster of C/EBP binding motifs with the aid of C/EBP α. The revelation of these two functions of RTA, together with its role in initiation of a transcriptional cascade that leads to transcription of all viral lytic genes, shows that RTA is a critical initiator and regulator of KSHV lytic DNA replication and viral propagation.

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Enterovirus 70 Receptor Utilization Is Controlled by Capsid Residues That Also Regulate Host Range and Cytopathogenicity

Journal of Virology ◽

10.1128/jvi.01569-06 ◽

2007 ◽

Vol 81 (16) ◽

pp. 8648-8655 ◽

Cited By ~ 10

Author(s):

Melissa Stewart Kim ◽

Vincent R. Racaniello

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Rhesus Monkey ◽

Host Range ◽

Hela Cells ◽

Lytic Replication ◽

Monkey Kidney ◽

Kidney Cells ◽

Cytopathic Effects ◽

Axis Of Symmetry

ABSTRACT Enterovirus type 70, an etiologic agent of acute hemorrhagic conjunctivitis, may bind different cellular receptors depending on cell type. To understand how EV70-receptor interaction is controlled, we studied two variants of the virus with distinct receptor utilization. EV70-Rmk, derived by passage in rhesus monkey kidney cells, replicates poorly in HeLa cells and does not cause cytopathic effects. Decay accelerating factor (DAF) is not a cell receptor for EV70-Rmk. Passage of EV70-Rmk in HeLa cells lead to isolation of EV70-Dne, which does not replicate in rhesus monkey kidney cells but grows to high titers in HeLa cells and causes cytopathic effects. DAF is sufficient for cell entry of EV70-Dne. EV70-Rmk replicates in human eye and brain-derived cell lines, whereas the Dne strain replicates only in HeLa cells and in conjunctiva-derived 15C4 cells. The two EV70 strains differ by five amino acid changes in the viral capsid. Single substitution of four of the five EV70-Rmk amino acids with the residue from EV70-Dne leads to lytic replication in HeLa cells. Conversely, substitution of any of the five EV70-Dne amino acids with the EV70-Rmk amino acid does not alter replication in HeLa cells. Three of these capsid amino acids are predicted to be located in the canyon encircling the fivefold axis of symmetry, one amino acid is found at the fivefold axis of symmetry, and one is located the interior of the capsid. The five EV70 residues define a region of the capsid that controls viral host range, DAF utilization, and cytopathogenicity.

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How to Train Your Phage: The Recent Efforts in Phage Training

Biologics ◽

10.3390/biologics1020005 ◽

2021 ◽

Vol 1 (2) ◽

pp. 70-88

Author(s):

Abdallah Abdelsattar ◽

Alyaa Dawooud ◽

Nouran Rezk ◽

Salsabil Makky ◽

Anan Safwat ◽

...

Keyword(s):

Host Range ◽

Pathogenic Bacteria ◽

Bacterial Resistance ◽

Phage Therapy ◽

Current Knowledge ◽

Lytic Replication ◽

Resistant Bacteria ◽

Infection Cycles ◽

Different Strains ◽

Specific Species

Control of pathogenic bacteria by deliberate application of predatory phages has potential as a powerful therapy against antibiotic-resistant bacteria. The key advantages of phage biocontrol over antibacterial chemotherapy are: (1) an ability to self-propagate inside host bacteria, (2) targeted predation of specific species or strains of bacteria, (3) adaptive molecular machinery to overcome resistance in target bacteria. However, realizing the potential of phage biocontrol is dependent on harnessing or adapting these responses, as many phage species switch between lytic infection cycles (resulting in lysis) and lysogenic infection cycles (resulting in genomic integration) that increase the likelihood of survival of the phage in response to external stress or host depletion. Similarly, host range will need to be optimized to make phage therapy medically viable whilst avoiding the potential for deleteriously disturbing the commensal microbiota. Phage training is a new approach to produce efficient phages by capitalizing on the evolved response of wild-type phages to bacterial resistance. Here we will review recent studies reporting successful trials of training different strains of phages to switch into lytic replication mode, overcome bacterial resistance, and increase their host range. This review will also highlight the current knowledge of phage training and future implications in phage applications and phage therapy and summarize the recent pipeline of the magistral preparation to produce a customized phage for clinical trials and medical applications.

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Lytic Replication-Defective Kaposi's Sarcoma-Associated Herpesvirus: Potential Role in Infection and Malignant Transformation

Journal of Virology ◽

10.1128/jvi.78.20.11108-11120.2004 ◽

2004 ◽

Vol 78 (20) ◽

pp. 11108-11120 ◽

Cited By ~ 14

Author(s):

Jian-Hong Deng ◽

Yan-Jin Zhang ◽

Xin-Ping Wang ◽

Shou-Jiang Gao

Keyword(s):

Malignant Transformation ◽

Cell Lines ◽

Kaposi's Sarcoma ◽

Potential Role ◽

Primary Effusion Lymphoma ◽

Kaposi’S Sarcoma ◽

Lytic Replication ◽

Screening Methods ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Defective viruses often have pivotal roles in virus-induced diseases. Although Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL), defective KSHV has not been reported. Using differential genetic screening methods, we show that defective KSHV is present in KS tumors and PEL cell lines. To investigate the role of defective viruses in KSHV-induced pathogenesis, we isolated and characterized a lytic replication-defective KSHV, KV-1, containing an 82-kb genomic deletion of solely lytic genes. Cells harboring KV-1 escaped G0/G1 apoptosis induced by spontaneous lytic replication occurred in cells infected with regular KSHV but maintained efficient latent replication. Consequently, KV-1-infected cells had phenotypes of enhanced cell proliferation and transformation potentials. Importantly, KV-1 was packaged as infectious virions by using regular KSHV as helpers, and KV-1-like variants were detected in cultures of two of five KSHV cell lines and 1 of 18 KS tumors. These results point to a potential role for defective viruses in the regulation of KSHV infection and malignant transformation.

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