Latency-associated nuclear antigen inhibits lytic replication of Kaposi's sarcoma-associated herpesvirus by regulating let-7a/RBPJ signaling

ABSTRACT The majority of Kaposi's sarcoma-associated herpesvirus (KSHV)-infected cells identified in vivo contain latent KSHV, with lytic replication in only a few percent of cells, as is the case for the cells of Kaposi's sarcoma (KS) lesions. Factors that influence KSHV latent or lytic replication are not well defined. Because persons with KS are often immunosuppressed and susceptible to many infectious agents, including human cytomegalovirus (HCMV), we have investigated the potential for HCMV to influence the replication of KSHV. Important to this work was the construction of a recombinant KSHV, rKSHV.152, expressing the green fluorescent protein (GFP) andneo (conferring resistance to G418). The expression of GFP was a marker of KSHV infection in cells of both epithelial and endothelial origin. The rKSHV.152 virus was used to establish cells, including human fibroblasts (HF), containing only latent KSHV, as demonstrated by latency-associated nuclear antigen expression and Gardella gel analysis. HCMV infection of KSHV latently infected HF activated KSHV lytic replication with the production of infectious KSHV. Dual-color immunofluorescence detected both the KSHV lytic open reading frame 59 protein and the HCMV glycoprotein B in coinfected cells, and UV-inactivated HCMV did not activate the production of infectious KSHV-GFP. In addition, HCMV coinfection increased the production of KSHV from endothelial cells and activated lytic cycle gene expression in keratinocytes. These data demonstrate that HCMV can activate KSHV lytic replication and suggest that HCMV could influence KSHV pathogenesis.

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Kaposi's Sarcoma-Associated Herpesvirus Latent Protein LANA Interacts with HIF-1α To Upregulate RTA Expression during Hypoxia: Latency Control under Low Oxygen Conditions

Journal of Virology ◽

10.1128/jvi.00689-06 ◽

2006 ◽

Vol 80 (16) ◽

pp. 7965-7975 ◽

Cited By ~ 92

Author(s):

Qiliang Cai ◽

Ke Lan ◽

Subhash C. Verma ◽

Huaxin Si ◽

Doug Lin ◽

...

Keyword(s):

Kaposi's Sarcoma ◽

Primary Effusion Lymphoma ◽

Kaposi’S Sarcoma ◽

Lytic Replication ◽

Nuclear Antigen ◽

Regulatory Sequences ◽

Physical Interaction ◽

Low Oxygen ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Hypoxia can induce lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) in primary effusion lymphoma (PEL) cells. However, the molecular mechanism of lytic reactivation of KSHV by hypoxia remains unclear. Here we show that the latency-associated nuclear antigen (LANA), which plays a crucial role in modulating viral and cellular gene expression, directly associated with a low oxygen responder, hypoxia-inducible factor-1α (HIF-1α). LANA enhanced not only the transcriptional activities of HIF-1α but also its mRNA level. Coimmunoprecipitation and immunofluorescence studies documented a physical interaction between LANA and HIF-1α in transiently transfected 293T cells as well as in PEL cell lines during hypoxia. Through sequence analysis, several putative hypoxia response elements (HRE-1 to -6) were identified in the essential lytic gene Rta promoter. Reporter assays showed that HRE-2 (−1130 to −1123) and HRE-5 and HRE-6 (+234 to +241 and +812 to +820, respectively, within the intron sequence) were necessary and sufficient for the LANA-mediated HIF-1α response. Electrophoretic mobility shift assays showed HIF-1α-dependent binding of a LANA protein complex specifically to the HRE-2, -5, and -6 motifs within the promoter regulatory sequences. This study demonstrates that hypoxia-induced KSHV lytic replication is mediated at least in part through cooperation of HIF-1α with LANA bound to the HRE motifs of the Rta promoter.

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Differential Regulation of the Overlapping Kaposi's Sarcoma-Associated Herpesvirus vGCR (orf74) and LANA (orf73) Promoters

Journal of Virology ◽

10.1128/jvi.75.4.1798-1807.2001 ◽

2001 ◽

Vol 75 (4) ◽

pp. 1798-1807 ◽

Cited By ~ 93

Author(s):

Joseph Jeong ◽

James Papin ◽

Dirk Dittmer

Keyword(s):

Kaposi's Sarcoma ◽

Regulatory Region ◽

Kaposi’S Sarcoma ◽

Lytic Replication ◽

Lytic Cycle ◽

Nuclear Antigen ◽

Barr Virus ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

High Level ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Similar to that of other herpesviruses, Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) lytic replication destroys the host cell, while the virus can persist in a latent state in synchrony with the host. During latency only a few genes are transcribed, and the question becomes one of what determines latent versus lytic gene expression. Here we undertake a detailed analysis of the latency-associated nuclear antigen (LANA [orf73]) promoter (LANAp). We characterized a minimal region that is necessary and sufficient to maintain high-level transcription in all tissues tested, including primary endothelial cells and B cells, which are the suspected natural host for KSHV. We show that in transient-transfection assays LANAp mimics the expression pattern observed for the authentic promoter in the context of the KSHV episome. Unlike other KSHV promoters tested thus far, LANAp is not affected by tetradecanoyl phorbol acetate or viral lytic cycle functions. It is, however, subject to control by LANA itself and cellular regulatory factors, such as p53. This is in contrast to the K14/vGCR (orf74) promoter, which overlaps LANAp and directs transcription on the opposite strand. We isolated a minimal cis-regulatory region sufficient for K14/vGCR promoter activity and show that it, too, mimics the regulation observed for the authentic viral promoter. In particular, we demonstrate that its activity is absolutely dependent on the immediate-early transactivator orf50, the KSHV homolog of the Epstein-Barr virus Rta transactivator.

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NDRG1 facilitates lytic replication of Kaposi’s sarcoma-associated herpesvirus by maintaining the stability of the KSHV helicase

PLoS Pathogens ◽

10.1371/journal.ppat.1009645 ◽

2021 ◽

Vol 17 (6) ◽

pp. e1009645

Author(s):

Lianghui Dong ◽

Jiazhen Dong ◽

Min Xiang ◽

Ping Lei ◽

Zixian Li ◽

...

Keyword(s):

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Dna Helicase ◽

Lytic Replication ◽

Nuclear Antigen ◽

Genome Replication ◽

Transcription Activator ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

The Stability ◽

Kaposi’S Sarcoma Associated Herpesvirus

The presumed DNA helicase encoded by ORF44 of Kaposi’s sarcoma-associated herpesvirus (KSHV) plays a crucial role in unwinding viral double-stranded DNA and initiating DNA replication during lytic reactivation. However, the regulatory mechanism of KSHV ORF44 has not been fully elucidated. In a previous study, we identified that N-Myc downstream regulated gene 1 (NDRG1), a host scaffold protein, facilitates viral genome replication by interacting with proliferating cell nuclear antigen (PCNA) and the latent viral protein latency-associated nuclear antigen (LANA) during viral latency. In the present study, we further demonstrated that NDRG1 can interact with KSHV ORF44 during viral lytic replication. We also found that the mRNA and protein levels of NDRG1 were significantly increased by KSHV ORF50-encoded replication and transcription activator (RTA). Remarkably, knockdown of NDRG1 greatly decreased the protein level of ORF44 and impaired viral lytic replication. Interestingly, NDRG1 enhanced the stability of ORF44 and inhibited its ubiquitin-proteasome-mediated degradation by reducing the polyubiquitination of the lysine residues at positions 79 and 368 in ORF44. In summary, NDRG1 is a novel binding partner of ORF44 and facilitates viral lytic replication by maintaining the stability of ORF44. This study provides new insight into the mechanisms underlying KSHV lytic replication.

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Long-Term-Infected Telomerase-Immortalized Endothelial Cells: a Model for Kaposi's Sarcoma-Associated Herpesvirus Latency In Vitro and In Vivo

Journal of Virology ◽

10.1128/jvi.80.10.4833-4846.2006 ◽

2006 ◽

Vol 80 (10) ◽

pp. 4833-4846 ◽

Cited By ~ 91

Author(s):

Feng-Qi An ◽

Hope Merlene Folarin ◽

Nicole Compitello ◽

Justin Roth ◽

Stanton L. Gerson ◽

...

Keyword(s):

Endothelial Cells ◽

Growth Factor ◽

Cell Lines ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Lytic Replication ◽

Nuclear Antigen ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) is associated with Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease. Most KS tumor cells are latently infected with KSHV and are of endothelial origin. While PEL-derived cell lines maintain KSHV indefinitely, all KS tumor-derived cells to date have lost viral genomes upon ex vivo cultivation. To study KSHV latency and tumorigenesis in endothelial cells, we generated telomerase-immortalized human umbilical vein endothelial (TIVE) cells. TIVE cells express all KSHV latent genes 48 h postinfection, and productive lytic replication could be induced by RTA/Orf50. Similar to prior models, infected cultures gradually lost viral episomes. However, we also obtained, for the first time, two endothelial cell lines in which KSHV episomes were maintained indefinitely in the absence of selection. Long-term KSHV maintenance correlated with loss of reactivation in response to RTA/Orf50 and complete oncogenic transformation. Long-term-infected TIVE cells (LTC) grew in soft agar and proliferated under reduced-serum conditions. LTC, but not parental TIVE cells, formed tumors in nude mice. These tumors expressed high levels of the latency-associated nuclear antigen (LANA) and expressed lymphatic endothelial specific antigens as found in KS (LYVE-1). Furthermore, host genes, like those encoding interleukin 6, vascular endothelial growth factor, and basic fibroblast growth factor, known to be highly expressed in KS lesions were also induced in LTC-derived tumors. KSHV-infected LTCs represent the first xenograft model for KS and should be of use to study KS pathogenesis and for the validation of anti-KS drug candidates.

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Full-Length Isoforms of Kaposi's Sarcoma-Associated Herpesvirus Latency-Associated Nuclear Antigen Accumulate in the Cytoplasm of Cells Undergoing the Lytic Cycle of Replication

Journal of Virology ◽

10.1128/jvi.01532-17 ◽

2017 ◽

Vol 91 (24) ◽

Cited By ~ 6

Author(s):

H. Jacques Garrigues ◽

Kellie Howard ◽

Serge Barcy ◽

Minako Ikoma ◽

Ashlee V. Moses ◽

...

Keyword(s):

Gene Expression ◽

Nuclear Localization ◽

Primary Infection ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Lytic Replication ◽

Lytic Cycle ◽

Nuclear Antigen ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT The latency-associated nuclear antigen (LANA) of the Kaposi's sarcoma-associated herpesvirus (KSHV) performs a variety of functions to establish and maintain KSHV latency. During latency, LANA localizes to discrete punctate spots in the nucleus, where it tethers viral episomes to cellular chromatin and interacts with nuclear components to regulate cellular and viral gene expression. Using highly sensitive tyramide signal amplification, we determined that LANA localizes to the cytoplasm in different cell types undergoing the lytic cycle of replication after de novo primary infection and after spontaneous, tetradecanoyl phorbol acetate-, or open reading frame 50 (ORF50)/replication transactivator (RTA)-induced activation. We confirmed the presence of cytoplasmic LANA in a subset of cells in lytically active multicentric Castleman disease lesions. The induction of cellular migration by scratch-wounding confluent cell cultures, culturing under subconfluent conditions, or induction of cell differentiation in primary cultures upregulated the number of cells permissive for primary lytic KSHV infection. The induction of lytic replication was characterized by high-level expression of cytoplasmic LANA and nuclear ORF59, a marker of lytic replication. Subcellular fractionation studies revealed the presence of multiple isoforms of LANA in the cytoplasm of ORF50/RTA-activated Vero cells undergoing primary infection. Mass spectrometry analysis demonstrated that cytoplasmic LANA isoforms were full length, containing the N-terminal nuclear localization signal. These results suggest that trafficking of LANA to different subcellular locations is a regulated phenomenon, which allows LANA to interact with cellular components in different compartments during both the latent and the replicative stages of the KSHV life cycle. IMPORTANCE Kaposi's sarcoma-associated herpesvirus (KSHV) causes AIDS-related malignancies, including lymphomas and Kaposi's sarcoma. KSHV establishes lifelong infections using its latency-associated nuclear antigen (LANA). During latency, LANA localizes to the nucleus, where it connects viral and cellular DNA complexes and regulates gene expression, allowing the virus to maintain long-term infections. Our research shows that intact LANA traffics to the cytoplasm of cells undergoing permissive lytic infections and latently infected cells in which the virus is induced to replicate. This suggests that LANA plays important roles in the cytoplasm and nuclear compartments of the cell during different stages of the KSHV life cycle. Determining cytoplasmic function and mechanism for regulation of the nuclear localization of LANA will enhance our understanding of the biology of this virus, leading to therapeutic approaches to eliminate infection and block its pathological effects.

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Kaposi's Sarcoma-Associated Herpesvirus-Encoded Latency-Associated Nuclear Antigen Inhibits Lytic Replication by Targeting Rta: a Potential Mechanism for Virus-Mediated Control of Latency

Journal of Virology ◽

10.1128/jvi.78.12.6585-6594.2004 ◽

2004 ◽

Vol 78 (12) ◽

pp. 6585-6594 ◽

Cited By ~ 146

Author(s):

Ke Lan ◽

Daniel A. Kuppers ◽

Subhash C. Verma ◽

Erle S. Robertson

Keyword(s):

Kaposi's Sarcoma ◽

Critical Role ◽

Human Herpesvirus ◽

Kaposi’S Sarcoma ◽

Lytic Replication ◽

Nuclear Antigen ◽

Viral Progeny ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Like other herpesviruses, Kaposi's sarcoma-associated herpesvirus (KSHV, also designated human herpesvirus 8) can establish a latent infection in the infected host. During latency a small number of genes are expressed. One of those genes encodes latency-associated nuclear antigen (LANA), which is constitutively expressed in cells during latent as well as lytic infection. LANA has previously been shown to be important for the establishment of latent episome maintenance through tethering of the viral genome to the host chromosomes. Under specific conditions, KSHV can undergo lytic replication, with the production of viral progeny. The immediate-early Rta, encoded by open reading frame 50 of KSHV, has been shown to play a critical role in switching from viral latent replication to lytic replication. Overexpression of Rta from a heterologous promoter is sufficient for driving KSHV lytic replication and the production of viral progeny. In the present study, we show that LANA down-modulates Rta's promoter activity in transient reporter assays, thus repressing Rta-mediated transactivation. This results in a decrease in the production of KSHV progeny virions. We also found that LANA interacts physically with Rta both in vivo and in vitro. Taken together, our results demonstrate that LANA can inhibit viral lytic replication by inhibiting expression as well as antagonizing the function of Rta. This suggests that LANA may play a critical role in maintaining latency by controlling the switch between viral latency and lytic replication.

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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 Latency-Associated Nuclear Antigen Induces a Strong Bend on Binding to Terminal Repeat DNA

Journal of Virology ◽

10.1128/jvi.79.21.13829-13836.2005 ◽

2005 ◽

Vol 79 (21) ◽

pp. 13829-13836 ◽

Cited By ~ 22

Author(s):

Lai-Yee Wong ◽

Angus C. Wilson

Keyword(s):

Dna Replication ◽

Kaposi's Sarcoma ◽

Kaposi’S Sarcoma ◽

Nuclear Antigen ◽

Major Groove ◽

Repeat Dna ◽

Initiation Of Dna Replication ◽

Kaposi's Sarcoma Associated Herpesvirus ◽

Kaposi’S Sarcoma Associated Herpesvirus ◽

Herpesvirus Genome

ABSTRACT During latency, the Kaposi's sarcoma-associated herpesvirus genome is maintained as a circular episome, replicating in synchrony with host chromosomes. Replication requires the latency-associated nuclear antigen (LANA) and an origin of latent DNA replication located in the viral terminal repeats, consisting of two LANA binding sites (LBSs) and a GC-rich sequence. Here, we show that the recruitment of a LANA dimer to high-affinity site LBS-1 bends DNA by 57° and towards the major groove. The cooccupancy of LBS-1 and lower-affinity LBS-2 induces a symmetrical bend of 110°. By changing the origin architecture, LANA may help to assemble a specific nucleoprotein structure important for the initiation of DNA replication.

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