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2.
PLoS Pathog ; 13(4): e1006335, 2017 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-28430817

RESUMEN

Kaposi Sarcoma Herpesvirus (KSHV), a γ2-herpesvirus and class 1 carcinogen, is responsible for at least three human malignancies: Kaposi Sarcoma (KS), Primary Effusion Lymphoma (PEL) and Multicentric Castleman's Disease (MCD). Its major nuclear latency protein, LANA, is indispensable for the maintenance and replication of latent viral DNA in infected cells. Although LANA is mainly a nuclear protein, cytoplasmic isoforms of LANA exist and can act as antagonists of the cytoplasmic DNA sensor, cGAS. Here, we show that cytosolic LANA also recruits members of the MRN (Mre11-Rad50-NBS1) repair complex in the cytosol and thereby inhibits their recently reported role in the sensing of cytoplasmic DNA and activation of the NF-κB pathway. Inhibition of NF-κB activation by cytoplasmic LANA is accompanied by increased lytic replication in KSHV-infected cells, suggesting that MRN-dependent NF-κB activation contributes to KSHV latency. Cytoplasmic LANA may therefore support the activation of KSHV lytic replication in part by counteracting the activation of NF-κB in response to cytoplasmic DNA. This would complement the recently described role of cytoplasmic LANA in blocking an interferon response triggered by cGAS and thereby promoting lytic reactivation. Our findings highlight a second point at which cytoplasmic LANA interferes with the innate immune response, as well as the importance of the recently discovered role of cytoplasmic MRN complex members as innate sensors of cytoplasmic DNA for the control of KSHV replication.


Asunto(s)
Antígenos Virales/inmunología , Replicación del ADN , Herpesvirus Humano 8/inmunología , FN-kappa B/metabolismo , Proteínas Nucleares/inmunología , Sarcoma de Kaposi/inmunología , Transducción de Señal , Replicación Viral , Ácido Anhídrido Hidrolasas , Antígenos Virales/genética , Antígenos Virales/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Citoplasma/metabolismo , Enzimas Reparadoras del ADN/genética , Enzimas Reparadoras del ADN/metabolismo , ADN Viral/genética , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Células HEK293 , Herpesvirus Humano 8/genética , Herpesvirus Humano 8/fisiología , Humanos , Inmunidad Innata , Proteína Homóloga de MRE11 , Modelos Biológicos , FN-kappa B/genética , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Isoformas de Proteínas , Sarcoma de Kaposi/virología , Latencia del Virus
3.
Proc Natl Acad Sci U S A ; 113(8): E1034-43, 2016 Feb 23.
Artículo en Inglés | MEDLINE | ID: mdl-26811480

RESUMEN

The latency-associated nuclear antigen (LANA) of Kaposi sarcoma herpesvirus (KSHV) is mainly localized and functions in the nucleus of latently infected cells, playing a pivotal role in the replication and maintenance of latent viral episomal DNA. In addition, N-terminally truncated cytoplasmic isoforms of LANA, resulting from internal translation initiation, have been reported, but their function is unknown. Using coimmunoprecipitation and MS, we found the cGMP-AMP synthase (cGAS), an innate immune DNA sensor, to be a cellular interaction partner of cytoplasmic LANA isoforms. By directly binding to cGAS, LANA, and particularly, a cytoplasmic isoform, inhibit the cGAS-STING-dependent phosphorylation of TBK1 and IRF3 and thereby antagonize the cGAS-mediated restriction of KSHV lytic replication. We hypothesize that cytoplasmic forms of LANA, whose expression increases during lytic replication, inhibit cGAS to promote the reactivation of the KSHV from latency. This observation points to a novel function of the cytoplasmic isoforms of LANA during lytic replication and extends the function of LANA from its role during latency to the lytic replication cycle.


Asunto(s)
Antígenos Virales/metabolismo , Citoplasma/metabolismo , Herpesvirus Humano 8/fisiología , Proteínas Nucleares/metabolismo , Nucleotidiltransferasas/antagonistas & inhibidores , Nucleotidiltransferasas/metabolismo , Replicación Viral/fisiología , Animales , Antígenos Virales/genética , Chlorocebus aethiops , Citoplasma/genética , Citoplasma/virología , Células HeLa , Humanos , Proteínas Nucleares/genética , Nucleotidiltransferasas/genética , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Células Vero
4.
J Virol ; 91(14)2017 07 15.
Artículo en Inglés | MEDLINE | ID: mdl-28446671

RESUMEN

Kaposi's sarcoma herpesvirus (KSHV) establishes lifelong latency. The viral latency-associated nuclear antigen (LANA) promotes viral persistence by tethering the viral genome to cellular chromosomes and by participating in latent DNA replication. Recently, the structure of the LANA C-terminal DNA binding domain was solved and new cytoplasmic variants of LANA were discovered. We discuss how these findings contribute to our current view of LANA structure and assembly and of its role during viral persistence.


Asunto(s)
Antígenos Virales/química , Antígenos Virales/metabolismo , Replicación del ADN , ADN Viral/metabolismo , Herpesvirus Humano 8/fisiología , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Latencia del Virus , Modelos Biológicos , Modelos Moleculares , Conformación Proteica
5.
Proc Natl Acad Sci U S A ; 112(21): 6694-9, 2015 May 26.
Artículo en Inglés | MEDLINE | ID: mdl-25947153

RESUMEN

Kaposi sarcoma herpesvirus (KSHV) persists as a latent nuclear episome in dividing host cells. This episome is tethered to host chromatin to ensure proper segregation during mitosis. For duplication of the latent genome, the cellular replication machinery is recruited. Both of these functions rely on the constitutively expressed latency-associated nuclear antigen (LANA) of the virus. Here, we report the crystal structure of the KSHV LANA DNA-binding domain (DBD) in complex with its high-affinity viral target DNA, LANA binding site 1 (LBS1), at 2.9 Šresolution. In contrast to homologous proteins such as Epstein-Barr virus nuclear antigen 1 (EBNA-1) of the related γ-herpesvirus Epstein-Barr virus, specific DNA recognition by LANA is highly asymmetric. In addition to solving the crystal structure, we found that apart from the two known LANA binding sites, LBS1 and LBS2, LANA also binds to a novel site, denoted LBS3. All three sites are located in a region of the KSHV terminal repeat subunit previously recognized as a minimal replicator. Moreover, we show that the LANA DBD can coat DNA of arbitrary sequence by virtue of a characteristic lysine patch, which is absent in EBNA-1 of the Epstein-Barr virus. Likely, these higher-order assemblies involve the self-association of LANA into supermolecular spirals. One such spiral assembly was solved as a crystal structure of 3.7 Šresolution in the absence of DNA. On the basis of our data, we propose a model for the controlled nucleation of higher-order LANA oligomers that might contribute to the characteristic subnuclear KSHV microdomains ("LANA speckles"), a hallmark of KSHV latency.


Asunto(s)
Antígenos Virales/química , Herpesvirus Humano 8/química , Proteínas Nucleares/química , Secuencia de Aminoácidos , Antígenos Virales/genética , Antígenos Virales/metabolismo , Secuencia de Bases , Sitios de Unión , Cristalografía por Rayos X , ADN Viral/genética , ADN Viral/metabolismo , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Herpesvirus Humano 8/genética , Herpesvirus Humano 8/metabolismo , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Estructura Cuaternaria de Proteína , Estructura Terciaria de Proteína , Dispersión del Ángulo Pequeño , Electricidad Estática , Difracción de Rayos X
6.
PLoS Pathog ; 11(8): e1005105, 2015 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-26295810

RESUMEN

Kaposi's sarcoma (KS), caused by Kaposi's sarcoma herpesvirus (KSHV), is a highly vascularised tumour of endothelial origin. KSHV infected endothelial cells show increased invasiveness and angiogenesis. Here, we report that the KSHV K15 protein, which we showed previously to contribute to KSHV-induced angiogenesis, is also involved in KSHV-mediated invasiveness in a PLCγ1-dependent manner. We identified ßPIX, GIT1 and cdc42, downstream effectors of PLCγ1 in cell migration, as K15 interacting partners and as contributors to KSHV-triggered invasiveness. We mapped the interaction between PLCγ1, PLCγ2 and their individual domains with two K15 alleles, P and M. We found that the PLCγ2 cSH2 domain, by binding to K15P, can be used as dominant negative inhibitor of the K15P-PLCγ1 interaction, K15P-dependent PLCγ1 phosphorylation, NFAT-dependent promoter activation and the increased invasiveness and angiogenic properties of KSHV infected endothelial cells. We increased the binding of the PLCγ2 cSH2 domain for K15P by substituting two amino acids, thereby creating an improved dominant negative inhibitor of the K15P-dependent PLCγ1 activation. Taken together, these results demonstrate a necessary role of K15 in the increased invasiveness and angiogenesis of KSHV infected endothelial cells and suggest the K15-PLCγ1 interaction as a possible new target for inhibiting the angiogenic and invasive properties of KSHV.


Asunto(s)
Invasividad Neoplásica/patología , Neovascularización Patológica/metabolismo , Fosfolipasa C gamma/metabolismo , Sarcoma de Kaposi/patología , Proteínas Virales/metabolismo , Western Blotting , Células Endoteliales , Técnica del Anticuerpo Fluorescente , Herpesvirus Humano 8/metabolismo , Humanos , Inmunoprecipitación , Neovascularización Patológica/patología , Sarcoma de Kaposi/metabolismo , Resonancia por Plasmón de Superficie , Transfección
7.
PLoS Pathog ; 9(10): e1003640, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-24146614

RESUMEN

Kaposi sarcoma-associated herpesvirus (KSHV) establishes a lifelong latent infection and causes several malignancies in humans. Murine herpesvirus 68 (MHV-68) is a related γ2-herpesvirus frequently used as a model to study the biology of γ-herpesviruses in vivo. The KSHV latency-associated nuclear antigen (kLANA) and the MHV68 mLANA (orf73) protein are required for latent viral replication and persistence. Latent episomal KSHV genomes and kLANA form nuclear microdomains, termed 'LANA speckles', which also contain cellular chromatin proteins, including BRD2 and BRD4, members of the BRD/BET family of chromatin modulators. We solved the X-ray crystal structure of the C-terminal DNA binding domains (CTD) of kLANA and MHV-68 mLANA. While these structures share the overall fold with the EBNA1 protein of Epstein-Barr virus, they differ substantially in their surface characteristics. Opposite to the DNA binding site, both kLANA and mLANA CTD contain a characteristic lysine-rich positively charged surface patch, which appears to be a unique feature of γ2-herpesviral LANA proteins. Importantly, kLANA and mLANA CTD dimers undergo higher order oligomerization. Using NMR spectroscopy we identified a specific binding site for the ET domains of BRD2/4 on kLANA. Functional studies employing multiple kLANA mutants indicate that the oligomerization of native kLANA CTD dimers, the characteristic basic patch and the ET binding site on the kLANA surface are required for the formation of kLANA 'nuclear speckles' and latent replication. Similarly, the basic patch on mLANA contributes to the establishment of MHV-68 latency in spleen cells in vivo. In summary, our data provide a structural basis for the formation of higher order LANA oligomers, which is required for nuclear speckle formation, latent replication and viral persistence.


Asunto(s)
Antígenos Virales/metabolismo , Cromatina/metabolismo , Herpesvirus Humano 8/fisiología , Proteínas Nucleares/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Rhadinovirus/fisiología , Factores de Transcripción/metabolismo , Proteínas Virales/metabolismo , Animales , Antígenos Virales/química , Antígenos Virales/genética , Proteínas de Ciclo Celular , Cromatina/genética , Cromatina/virología , Proteínas Cromosómicas no Histona , Cristalografía por Rayos X , Células HEK293 , Células HeLa , Herpesvirus Humano 8/química , Humanos , Ratones , Proteínas Nucleares/química , Proteínas Nucleares/genética , Multimerización de Proteína , Proteínas Serina-Treonina Quinasas/química , Proteínas Serina-Treonina Quinasas/genética , Estructura Cuaternaria de Proteína , Rhadinovirus/química , Bazo/metabolismo , Bazo/virología , Relación Estructura-Actividad , Factores de Transcripción/química , Factores de Transcripción/genética , Proteínas Virales/química , Proteínas Virales/genética , Latencia del Virus/fisiología
8.
PLoS Pathog ; 9(11): e1003737, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-24244164

RESUMEN

Kaposi's sarcoma (KS) is a mesenchymal tumour, which is caused by Kaposi's sarcoma herpesvirus (KSHV) and develops under inflammatory conditions. KSHV-infected endothelial spindle cells, the neoplastic cells in KS, show increased invasiveness, attributed to the elevated expression of metalloproteinases (MMPs) and cyclooxygenase-2 (COX-2). The majority of these spindle cells harbour latent KSHV genomes, while a minority undergoes lytic reactivation with subsequent production of new virions and viral or cellular chemo- and cytokines, which may promote tumour invasion and dissemination. In order to better understand KSHV pathogenesis, we investigated cellular mechanisms underlying the lytic reactivation of KSHV. Using a combination of small molecule library screening and siRNA silencing we found a STE20 kinase family member, MAP4K4, to be involved in KSHV reactivation from latency and to contribute to the invasive phenotype of KSHV-infected endothelial cells by regulating COX-2, MMP-7, and MMP-13 expression. This kinase is also highly expressed in KS spindle cells in vivo. These findings suggest that MAP4K4, a known mediator of inflammation, is involved in KS aetiology by regulating KSHV lytic reactivation, expression of MMPs and COX-2, and, thereby modulating invasiveness of KSHV-infected endothelial cells.


Asunto(s)
Células Endoteliales/metabolismo , Regulación Enzimológica de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Herpesvirus Humano 8/fisiología , Péptidos y Proteínas de Señalización Intracelular/biosíntesis , Proteínas de Neoplasias/biosíntesis , Proteínas Serina-Treonina Quinasas/biosíntesis , Sarcoma de Kaposi/metabolismo , Activación Viral/fisiología , Ciclooxigenasa 2/biosíntesis , Ciclooxigenasa 2/genética , Células Endoteliales/patología , Células Endoteliales/virología , Femenino , Células HEK293 , Humanos , Inflamación/genética , Inflamación/metabolismo , Inflamación/patología , Inflamación/virología , Péptidos y Proteínas de Señalización Intracelular/genética , Masculino , Metaloproteinasa 13 de la Matriz/biosíntesis , Metaloproteinasa 13 de la Matriz/genética , Metaloproteinasa 7 de la Matriz/biosíntesis , Metaloproteinasa 7 de la Matriz/genética , Invasividad Neoplásica/genética , Invasividad Neoplásica/patología , Proteínas de Neoplasias/genética , Proteínas Serina-Treonina Quinasas/genética , Sarcoma de Kaposi/genética , Sarcoma de Kaposi/patología
9.
J Virol ; 87(14): 8004-16, 2013 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-23678173

RESUMEN

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic herpesvirus and the cause of Kaposi's sarcoma, primary effusion lymphoma (PEL) and multicentric Castleman's disease. Latently infected B cells are the main reservoir of this virus in vivo, but the nature of the stimuli that lead to its reactivation in B cells is only partially understood. We established stable BJAB cell lines harboring latent KSHV by cell-free infection with recombinant virus carrying a puromycin resistance marker. Our latently infected B cell lines, termed BrK.219, can be reactivated by triggering the B cell receptor (BCR) with antibodies to surface IgM, a stimulus imitating antigen recognition. Using this B cell model system we studied the mechanisms that mediate the reactivation of KSHV in B cells following the stimulation of the BCR and could identify phosphatidylinositol 3-kinase (PI3K) and X-box binding protein 1 (XBP-1) as proteins that play an important role in the BCR-mediated reactivation of latent KSHV.


Asunto(s)
Linfocitos B/virología , Herpesvirus Humano 8/fisiología , Receptores de Antígenos de Linfocitos B/metabolismo , Activación Viral/fisiología , Latencia del Virus/fisiología , Animales , Anticuerpos Antiidiotipos/metabolismo , Línea Celular Tumoral , Chlorocebus aethiops , Inmunoprecipitación de Cromatina , Cartilla de ADN/genética , Proteínas de Unión al ADN/metabolismo , Técnica del Anticuerpo Fluorescente , Células HEK293 , Humanos , Immunoblotting , Fosfatidilinositol 3-Quinasa/metabolismo , Reacción en Cadena de la Polimerasa , Factores de Transcripción del Factor Regulador X , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Sales de Tetrazolio , Tiazoles , Factores de Transcripción/metabolismo , Células Vero , Proteína 1 de Unión a la X-Box
10.
J Virol ; 87(23): 12721-36, 2013 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-24049186

RESUMEN

Retroviral integrase (IN) proteins catalyze the permanent integration of proviral genomes into host DNA with the help of cellular cofactors. Lens epithelium-derived growth factor (LEDGF) is a cofactor for lentiviruses, including human immunodeficiency virus type 1 (HIV-1), and targets lentiviral integration toward active transcription units in the host genome. In contrast to lentiviruses, murine leukemia virus (MLV), a gammaretrovirus, tends to integrate near transcription start sites. Here, we show that the bromodomain and extraterminal domain (BET) proteins BRD2, BRD3, and BRD4 interact with gammaretroviral INs and stimulate the catalytic activity of MLV IN in vitro. We mapped the interaction site to a characteristic structural feature within the BET protein extraterminal (ET) domain and to three amino acids in MLV IN. The ET domains of different BET proteins stimulate MLV integration in vitro and, in the case of BRD2, also in vivo. Furthermore, two small-molecule BET inhibitors, JQ1 and I-BET, decrease MLV integration and shift it away from transcription start sites. Our data suggest that BET proteins might act as chromatin-bound acceptors for the MLV preintegration complex. These results could pave a way to redirecting MLV DNA integration as a basis for creating safer retroviral vectors.


Asunto(s)
Cromatina/metabolismo , Virus de la Leucemia Murina/fisiología , Proteínas Nucleares/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas de Unión al ARN/metabolismo , Infecciones por Retroviridae/metabolismo , Factores de Transcripción/metabolismo , Integración Viral , Secuencias de Aminoácidos , Animales , Proteínas de Ciclo Celular , Línea Celular , Células HEK293 , Humanos , Integrasas/genética , Integrasas/metabolismo , Virus de la Leucemia Murina/enzimología , Virus de la Leucemia Murina/genética , Ratones , Proteínas Nucleares/química , Proteínas Nucleares/genética , Unión Proteica , Proteínas Serina-Treonina Quinasas/química , Proteínas Serina-Treonina Quinasas/genética , Estructura Terciaria de Proteína , Proteínas de Unión al ARN/química , Proteínas de Unión al ARN/genética , Infecciones por Retroviridae/genética , Infecciones por Retroviridae/virología , Factores de Transcripción/química , Factores de Transcripción/genética , Proteínas Virales/genética , Proteínas Virales/metabolismo
11.
J Virol ; 86(12): 6745-57, 2012 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-22514345

RESUMEN

Kaposi's sarcoma herpesvirus (KSHV) belongs to the gamma-2 Herpesviridae and is associated with three neoplastic disorders: Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD). The viral latency-associated nuclear antigen 1 (LANA) is expressed in all latently KSHV-infected cells and is involved in viral latent replication and maintenance of the viral genome. We show that LANA interacts with the ubiquitin-specific protease USP7 through its N-terminal TRAF (tumor necrosis factor [TNF] receptor-associated factor) domain. This interaction involves a short sequence (amino acids [aa] 971 to 986) within the C-terminal domain of LANA with strong similarities to the USP7 binding site of the Epstein-Barr virus (EBV) EBNA-1 protein. A LANA mutant with a deletion of the identified USP7 binding site showed an enhanced ability to replicate a plasmid containing the KSHV latent origin of replication but was comparable to the wild-type LANA (LANA WT) with regard to the regulation of viral and cellular promoters. Furthermore, the LANA homologues of two other gamma-2 herpesviruses, MHV68 and RRV, also recruit USP7. Our findings suggest that recruitment of USP7 to LANA could play a role in the regulation of viral latent replication. The recruitment of USP7, and its role in herpesvirus latent replication, previously described for the latent EBNA-1 protein of the gamma-1 herpesvirus (lymphocryptovirus) EBV (M. N. Holowaty et al., J. Biol. Chem. 278:29987-29994, 2003), may thereby be a conserved feature among gammaherpesvirus latent origin binding proteins.


Asunto(s)
ADN Viral/genética , Infecciones por Herpesviridae/enzimología , Infecciones por Herpesviridae/virología , Herpesvirus Humano 8/fisiología , Ubiquitina Tiolesterasa/metabolismo , Latencia del Virus , Replicación Viral , Antígenos Virales/genética , Antígenos Virales/metabolismo , Línea Celular , ADN Viral/metabolismo , Infecciones por Herpesviridae/genética , Herpesvirus Humano 8/genética , Humanos , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Unión Proteica , Ubiquitina Tiolesterasa/genética , Peptidasa Específica de Ubiquitina 7 , Proteínas Virales/genética , Proteínas Virales/metabolismo
12.
PLoS Pathog ; 5(3): e1000324, 2009 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-19266083

RESUMEN

Host signal-transduction pathways are intimately involved in the switch between latency and productive infection of herpes viruses. As with other herpes viruses, infection by Kaposi's sarcoma herpesvirus (KSHV) displays these two phases. During latency only few viral genes are expressed, while in the productive infection the virus is reactivated with initiation of extensive viral DNA replication and gene expression, resulting in production of new viral particles. Viral reactivation is crucial for KSHV pathogenesis and contributes to the progression of KS. We have recently identified Pim-1 as a kinase reactivating KSHV upon over-expression. Here we show that another Pim family kinase, Pim-3, also induces viral reactivation. We demonstrate that expression of both Pim-1 and Pim-3 is induced in response to physiological and chemical reactivation in naturally KSHV-infected cells, and we show that they are required for KSHV reactivation under these conditions. Furthermore, our data indicate that Pim-1 and Pim-3 contribute to viral reactivation by phosphorylating the KSHV latency-associated nuclear antigen (LANA) on serine residues 205 and 206. This counteracts the LANA-mediated repression of the KSHV lytic gene transcription. The identification of Pim family kinases as novel cellular regulators of the gammaherpesvirus life cycle facilitates a deeper understanding of virus-host interactions during reactivation and may represent potential novel targets for therapeutic intervention.


Asunto(s)
Antígenos Virales/metabolismo , Herpesvirus Humano 8/fisiología , Proteínas Nucleares/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-pim-1/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Activación Viral , Latencia del Virus , Animales , Línea Celular Tumoral , Chlorocebus aethiops , Regulación Viral de la Expresión Génica , Interacciones Huésped-Patógeno , Humanos , Interferón gamma/metabolismo , Fosforilación , Proteínas Serina-Treonina Quinasas/genética , Proteínas Proto-Oncogénicas/genética , Proteínas Proto-Oncogénicas c-pim-1/genética , ARN Interferente Pequeño/metabolismo , Transducción de Señal , Células Vero , Replicación Viral
13.
Pathogens ; 9(2)2020 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-32075270

RESUMEN

Latency establishment is the hallmark feature of herpesviruses, a group of viruses, of which nine are known to infect humans. They have co-evolved alongside their hosts, and mastered manipulation of cellular pathways and tweaking various processes to their advantage. As a result, they are very well adapted to persistence. The members of the three subfamilies belonging to the family Herpesviridae differ with regard to cell tropism, target cells for the latent reservoir, and characteristics of the infection. The mechanisms governing the latent state also seem quite different. Our knowledge about latency is most complete for the gammaherpesviruses due to previously missing adequate latency models for the alpha and beta-herpesviruses. Nevertheless, with advances in cell biology and the availability of appropriate cell-culture and animal models, the common features of the latency in the different subfamilies began to emerge. Three criteria have been set forth to define latency and differentiate it from persistent or abortive infection: 1) persistence of the viral genome, 2) limited viral gene expression with no viral particle production, and 3) the ability to reactivate to a lytic cycle. This review discusses these criteria for each of the subfamilies and highlights the common strategies adopted by herpesviruses to establish latency.

14.
Front Microbiol ; 11: 591778, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33193257

RESUMEN

The rhadinoviruses Kaposi's Sarcoma-associated herpesvirus (KSHV) and murine gammaherpesvirus (MHV-68) persist in infected hosts in a latent state that is characterized by the absence of virus production and by restricted viral gene expression. Their major latency protein, the latency-associated nuclear antigen (kLANA for KSHV and mLANA for MHV-68), is essential for viral genome maintenance and replication and involved in transcriptional regulation. Both kLANA and mLANA interact with cellular chromatin-associated proteins, among them the Bromodomain and Extra Terminal domain (Brd/BET) proteins, which recruit cellular and viral proteins to acetylated histones through their bromodomains and modulate cellular gene expression. Brd/BET proteins also play a role in the tethering, replication, segregation or integration of a diverse group of viral DNA genomes. In this study we explored if Brd/BET proteins influence the localization of the LANAs to preferential regions in the host chromatin and thereby contribute to kLANA- or mLANA-mediated transcriptional regulation. Using ChIP-Seq, we revealed a genome-wide co-enrichment of kLANA with Brd2/4 near cellular and viral transcriptional start sites (TSS). Treatment with I-BET151, an inhibitor of Brd/BET, displaced kLANA and Brd2/4 from TSS in the viral and host chromatin, but did not affect the direct binding of kLANA to kLANA-binding sites (LBS) in the KSHV latent origin of replication. Similarly, mLANA, but not a mLANA mutant deficient for binding to Brd2/4, also associated with cellular TSS. We compared the transcriptome of KSHV-infected with uninfected and kLANA-expressing human B cell lines, as well as a murine B cell line expressing mLANA or a Brd2/4-binding deficient mLANA mutant. We found that only a minority of cellular genes, whose TSS are occupied by kLANA or mLANA, is transcriptionally regulated by these latency proteins. Our findings extend previous reports on a preferential deposition of kLANA on cellular TSS and show that this characteristic chromatin association pattern is at least partially determined by the interaction of these viral latency proteins with members of the Brd/BET family of chromatin modulators.

15.
Front Biosci (Landmark Ed) ; 15(2): 537-49, 2010 01 01.
Artículo en Inglés | MEDLINE | ID: mdl-20036832

RESUMEN

The bromodomain and ET domain (BET) proteins belong to a group of bromodomain proteins and bind acetylated histones. Two of the currently known members of this protein family were implicated in transcriptional regulation. The two most studied BET proteins Brd2 and Brd4 have been shown to bind to viral proteins of herpesviruses and papillomaviruses. These pathogens often take advantage of the cellular function of the BET proteins and exploit it for their own purposes. In some cases though, viral proteins were shown to adapt BET proteins to new virus specific functions. Additionally some retroviruses seem to encode proteins that mimic Brd4 functions and hijack Brd4-associated protein complexes to use them for their own transcription.


Asunto(s)
Antígenos Virales/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Factores de Transcripción/metabolismo , Animales , Antígenos Virales/genética , Sitios de Unión/genética , Proteínas de Ciclo Celular , Regulación Viral de la Expresión Génica , Herpesvirus Humano 8/genética , Herpesvirus Humano 8/metabolismo , Humanos , Proteínas Nucleares/genética , Unión Proteica , Proteínas Serina-Treonina Quinasas/genética , Sarcoma de Kaposi/genética , Sarcoma de Kaposi/metabolismo , Sarcoma de Kaposi/virología , Factores de Transcripción/genética
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