scholarly journals ORF57 Overcomes the Detrimental Sequence Bias of Kaposi's Sarcoma-Associated Herpesvirus Lytic Genes

2015 ◽  
Vol 89 (9) ◽  
pp. 5097-5109 ◽  
Author(s):  
Carolin Vogt ◽  
Christian Hackmann ◽  
Alona Rabner ◽  
Lars Koste ◽  
Susann Santag ◽  
...  
Keyword(s):  
Kaposi's Sarcoma ◽  
Rna Binding ◽  
Kaposi’S Sarcoma ◽  
Target Sequence ◽  
Nucleotide Bias ◽  
Viral Rnas ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Lytic Genes ◽  
Sequence Bias

ABSTRACTKaposi's sarcoma-associated herpesvirus (KSHV) encodes ORF57, which enhances the expression of intronless KSHV genes on multiple posttranscriptional levels. However, it remains elusive how ORF57 recognizes viral RNAs. Here, we demonstrate that ORF57 also increases the expression of the multiple intron-containing K15 gene. The nucleotide bias of the K15 cDNA revealed an unusual high AT content. Thus, we optimized the K15 cDNA by raising the frequency of GC nucleotides, yielding an ORF57-independent version. To further prove the importance of the sequence bias of ORF57-dependent RNAs, we grouped KSHV mRNAs according to their AT content and found a correlation between AT-richness and ORF57 dependency. More importantly, latent genes, which have to be expressed in the absence of ORF57, have a low AT content and are indeed ORF57 independent. The nucleotide composition of K15 resembles that of HIVgag, which cannot be expressed unless RNA export is facilitated by the HIV Rev protein. Interestingly, ORF57 can partially rescue HIV Gag expression. Thus, the KSHV target RNAs of ORF57 and HIVgagRNA may share certain motifs based on the nucleotide bias. A bioinformatic comparison between wild-type and sequence-optimized K15 revealed a higher density for hnRNP-binding motifs in the former. We speculate that binding of particular hnRNPs to KSHV lytic transcripts is the prerequisite for ORF57 to enhance their expression.IMPORTANCEThe mostly intronless genes of KSHV are only expressed in the presence of the viral regulator protein ORF57, but how ORF57 recognizes viral RNAs remains elusive. We focused on the multiple intron-containing KSHV gene K15 and revealed that its expression is also increased by ORF57. Moreover, sequences in the K15 cDNA mediate this enhancement. The quest for a target sequence or a response element for ORF57 in the lytic genes was not successful. Instead, we found the nucleotide bias to be the critical determinant of ORF57 dependency. Based on the fact that ORF57 has only a weak affinity for nucleic acids, we speculate that a cellular RNA-binding protein provides the sequence preference for ORF57. This study provides evidence that herpesviral RNA regulator proteins use the sequence bias of lytic genes and the resulting composition of the viral mRNP to distinguish between viral and cellular mRNAs.

scholarly journals Proteomic Analysis of the Kaposi's Sarcoma-Associated Herpesvirus Terminal Repeat Element Binding Proteins

2006 ◽  
Vol 80 (18) ◽  
pp. 9017-9030 ◽  
Author(s):  
Huaxin Si ◽  
Subhash C. Verma ◽  
Erle S. Robertson
Keyword(s):  
Proteomic Analysis ◽  
Kaposi's Sarcoma ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Kaposi’S Sarcoma ◽  
Terminal Repeat ◽  
Genome Maintenance ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Terminal repeat (TR) elements of Kaposi's sarcoma-associated herpesvirus (KSHV), the potential origin sites of KSHV replication, have been demonstrated to play important roles in viral replication and transcription and are most likely also critical for the segregation of the KSHV genome to daughter cells. To search for the cellular proteins potentially involved in KSHV genome maintenance, we performed affinity chromatography analysis, using KSHV TR DNA as the affinity ligand. Proteomic analysis was then carried out to identify the TR-interacting proteins. We identified a total of 123 proteins from both KSHV-positive and -negative cells, among which most were identified exclusively from KSHV-positive cells. These proteins were categorized as proliferation/cell cycle regulatory proteins, proteins involved in spliceosome components, such as heterogeneous nuclear ribonuclear proteins, the DEAD/H family, the switch/sucrose nonfermenting protein family, splicing factors, RNA binding proteins, transcription regulation proteins, replication factors, modifying enzymes, and a number of proteins that could not be broadly categorized. To support the proteomic results, the presence of four candidate proteins, ATR, BRG1, NPM1 and PARP-1, in the elutions was further characterized in this study. The binding and colocalization of these proteins with the TR were verified using chromatin immunoprecipitation and immunofluorescence in situ hybridization analysis. These newly identified TR binding proteins provide a number of clues and potential links to understanding the mechanisms regulating the replication, transcription, and genome maintenance of KSHV. This study will facilitate the generation and testing of new hypotheses to further our understanding of the mechanisms involved in KSHV persistence and its associated pathogenesis.

scholarly journals Binding of Cellular Export Factor REF/Aly by Kaposi's Sarcoma-Associated Herpesvirus (KSHV) ORF57 Protein Is Not Required for Efficient KSHV Lytic Replication

2012 ◽  
Vol 86 (18) ◽  
pp. 9866-9874 ◽  
Author(s):  
Da-Jiang Li ◽  
Dinesh Verma ◽  
Sankar Swaminathan
Keyword(s):  
Gene Expression ◽  
Nuclear Export ◽  
Kaposi's Sarcoma ◽  
Rna Binding ◽  
Virus Production ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Viral Mrnas ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) ORF57 protein is expressed early during lytic KSHV replication, enhances expression of many KSHV genes, and is essential for virus production. ORF57 is a member of a family of proteins conserved among all human and many animal herpesviruses that are multifunctional regulators of gene expression and act posttranscriptionally to increase accumulation of their target mRNAs. The mechanism of ORF57 action is complex and may involve effects on mRNA transcription, stability, and export. ORF57 directly binds to REF/Aly, a cellular RNA-binding protein component of the TREX complex that mediates RNA transcription and export. We analyzed the effects of an ORF57 mutation known to abrogate REF/Aly binding and demonstrate that the REF-binding mutant is impaired in activation of viral mRNAs and noncoding RNAs confined to the nucleus. Although the inability to bind REF leads to decreased ORF57 activity in enhancing gene expression, there is no demonstrable effect on nuclear export of viral mRNA or the ability of ORF57 to support KSHV replication and virus production. These data indicate that REF/Aly-ORF57 interaction is not essential for KSHV lytic replication but may contribute to target RNA stability independent of effects on RNA export, suggesting a novel role for REF/Aly in viral RNA metabolism.

scholarly journals Increased Efficiency of Phorbol Ester-Induced Lytic Reactivation of Kaposi's Sarcoma-Associated Herpesvirus during S Phase

2005 ◽  
Vol 79 (4) ◽  
pp. 2626-2630 ◽  
Author(s):  
Shane C. McAllister ◽  
Scott G. Hansen ◽  
Ilhem Messaoudi ◽  
Janko Nikolich-Zugich ◽  
Ashlee V. Moses
Keyword(s):  
Phorbol Ester ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
S Phase ◽  
Progeny Virus ◽  
Lytic Reactivation ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Lytic Genes

ABSTRACT Expression of Kaposi's sarcoma-associated herpesvirus (KSHV) lytic genes is thought to be essential for the establishment and progression of KSHV-induced diseases. The inefficiency of lytic reactivation in various in vitro systems hampers the study of lytic genes in the context of whole virus. We report here increased expression of KSHV lytic genes and increased release of progeny virus when synchronized cultures of body cavity-based lymphoma-1 cells are treated with a phorbol ester during S phase of the cell cycle.

scholarly journals High Glucose Induces Reactivation of Latent Kaposi's Sarcoma-Associated Herpesvirus

2016 ◽  
Vol 90 (21) ◽  
pp. 9654-9663 ◽  
Author(s):  
Fengchun Ye ◽  
Yan Zeng ◽  
Jingfeng Sha ◽  
Tiffany Jones ◽  
Kurt Kuhne ◽  
...  
Keyword(s):  
High Glucose ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Diabetic Patients ◽  
Glucose Levels ◽  
Production Of Hydrogen ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Lytic Genes

ABSTRACT A high prevalence of Kaposi's sarcoma (KS) is seen in diabetic patients. It is unknown if the physiological conditions of diabetes contribute to KS development. We found elevated levels of viral lytic gene expression when Kaposi's sarcoma-associated herpesvirus (KSHV)-infected cells were cultured in high-glucose medium. To demonstrate the association between high glucose levels and KSHV replication, we xenografted telomerase-immortalized human umbilical vein endothelial cells that are infected with KSHV (TIVE-KSHV cells) into hyperglycemic and normal nude mice. The injected cells expressed significantly higher levels of KSHV lytic genes in hyperglycemic mice than in normal mice. We further demonstrated that high glucose levels induced the production of hydrogen peroxide (H 2 O 2 ), which downregulated silent information regulator 1 (SIRT1), a class III histone deacetylase (HDAC), resulting in the epigenetic transactivation of KSHV lytic genes. These results suggest that high blood glucose levels in diabetic patients contribute to the development of KS by promoting KSHV lytic replication and infection. IMPORTANCE Multiple epidemiological studies have reported a higher prevalence of classic KS in diabetic patients. By using both in vitro and in vivo models, we demonstrated an association between high glucose levels and KSHV lytic replication. High glucose levels induce oxidative stress and the production of H 2 O 2 , which mediates the reactivation of latent KSHV through multiple mechanisms. Our results provide the first experimental evidence and mechanistic support for the association of classic KS with diabetes.

scholarly journals Suppression of Kaposi's Sarcoma-Associated Herpesvirus Infection and Replication by 5′-AMP-Activated Protein Kinase

2016 ◽  
Vol 90 (14) ◽  
pp. 6515-6525 ◽  
Author(s):  
Fan Cheng ◽  
Meilan He ◽  
Jae U. Jung ◽  
Chun Lu ◽  
Shou-Jiang Gao
Keyword(s):  
Protein Kinase ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Energy Sensor ◽  
Ampk Activity ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Amp Activated Protein Kinase ◽  
Lytic Genes

ABSTRACTThe host intracellular antiviral restriction factors inhibit viral infection and replication. The 5′-AMP-activated protein kinase (AMPK) is a cellular energy sensor regulating metabolic homeostasis. Activated AMPK inhibits the replication of numerous RNA viruses but enhances the entry of vaccinia virus. However, the role of AMPK in herpesvirus infection is unclear. In this study, we showed that the constitutive AMPK activity restricted Kaposi's sarcoma-associated herpesvirus (KSHV) lytic replication in primary human umbilical vein endothelial cells while KSHV infection did not markedly affect the endogenous AMPK activity. Knockdown of the AMPKα1 considerably enhanced the expression of viral lytic genes and the production of infectious virions, while overexpression of a constitutively active AMPK had the opposite effects. Accordingly, an AMPK inhibitor, compound C, augmented viral lytic gene expressions and virion productions but an AMPK agonist, 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), suppressed both. Furthermore, a common diabetes drug, metformin, which carries an AMPK-agonistic activity, drastically inhibited the expression of viral lytic genes and the production of infectious virions, suggesting the use of metformin as a therapeutic agent for KSHV infection and replication. Together, these results identify the host AMPK as a KSHV restriction factor that can serve as a potential therapeutic target.IMPORTANCEHost cells encode specific proteins to restrict viral infection and replication. Kaposi's sarcoma-associated herpesvirus (KSHV) is a human tumor virus associated with several cancers. In this study, we have identified 5′-AMP-activated protein kinase (AMPK), a cellular energy sensor, as a restriction factor of KSHV lytic replication during primary infection. Activation of AMPK suppresses, while inhibition of AMPK enhances, KSHV lytic replication by regulating the expression of viral genes. AICAR and metformin, both of which are AMPK agonists currently used in clinics for the treatment of conditions associated with metabolic disorders, inhibit KSHV lytic replication. Thus, our work has identified AMPK as a potential therapeutic target and AICAR and metformin as potential therapeutic agents for KSHV-associated cancers.

scholarly journals RNA Granules in Antiviral Innate Immunity: A Kaposi’s Sarcoma-Associated Herpesvirus Journey

2022 ◽  
Vol 12 ◽  
Author(s):  
Nishi R. Sharma ◽  
Zhi-Ming Zheng
Keyword(s):  
Innate Immunity ◽  
Kaposi's Sarcoma ◽  
Rna Binding ◽  
Kaposi’S Sarcoma ◽  
Productive Infection ◽  
Dna Virus ◽  
Rna Granules ◽  
Infected Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

RNA granules are cytoplasmic, non-membranous ribonucleoprotein compartments that form ubiquitously and are often referred to as foci for post-transcriptional gene regulation. Recent research on RNA processing bodies (PB) and stress granules (SG) has shown wide implications of these cytoplasmic RNA granules and their components in suppression of RNA translation as host intracellular innate immunity against infecting viruses. Many RNA viruses either counteract or co-opt these RNA granules; however, many fundamental questions about DNA viruses with respect to their interaction with these two RNA granules remain elusive. Kaposi’s sarcoma-associated herpesvirus (KSHV), a tumor-causing DNA virus, exhibits two distinct phases of infection and encodes ∼90 viral gene products during the lytic phase of infection compared to only a few (∼5) during the latent phase. Thus, productive KSHV infection relies heavily on the host cell translational machinery, which often links to the formation of PB and SG. One major question is how KSHV counteracts the hostile environment of RNA granules for its productive infection. Recent studies demonstrated that KSHV copes with the translational suppression by cellular RNA granules, PB and SG, by expressing ORF57, a viral RNA-binding protein, during KSHV lytic infection. ORF57 interacts with Ago2 and GW182, two major components of PB, and prevents the scaffolding activity of GW182 at the initial stage of PB formation in the infected cells. ORF57 also interacts with protein kinase R (PKR) and PKR-activating protein (PACT) to block PKR dimerization and kinase activation, and thus inhibits eIF2α phosphorylation and SG formation. The homologous immediate-early regulatory protein ICP27 of herpes simplex virus type 1 (HSV-1), but not the EB2 protein of Epstein-Barr virus (EBV), shares this conserved inhibitory function with KSHV ORF57 on PB and SG. Through KSHV ORF57 studies, we have learned much about how a DNA virus in the infected cells is equipped to evade host antiviral immunity for its replication and productive infection. KSHV ORF57 would be an excellent viral target for development of anti-KSHV-specific therapy.

Sign in / Sign up

Export Citation Format

Share Document