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

2006 ◽  
Vol 80 (24) ◽  
pp. 12171-12186 ◽  
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.

scholarly journals Potent Antiviral Activity of Topoisomerase I and II Inhibitors against Kaposi's Sarcoma-Associated Herpesvirus

2011 ◽  
Vol 56 (2) ◽  
pp. 893-902 ◽  
Author(s):  
Lorenzo González-Molleda ◽  
Yan Wang ◽  
Yan Yuan
Keyword(s):  
Dna Replication ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Cellular Proteins ◽  
Virion Production ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Topo Ii ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Lytic Dna Replication

ABSTRACTThe lytic DNA replication of Kaposi's sarcoma-associated herpesvirus (KSHV) initiates at an origin (ori-Lyt) and requirestrans-acting elements, both viral and cellular. We recently demonstrated that several host cellular proteins, including topoisomerases I and II (Topo I and II), are involved in KSHV lytic DNA replication (Y. Wang, H. Li, Q. Tang, G. G. Maul, and Y. Yuan. J. Virol. 82: 2867–2882, 2008). To assess the importance of these topoisomerases in viral lytic replication, shRNA-mediated gene silencing was used. Depletion of Topo I and II severely inhibited viral lytic DNA replication as well as virion production, suggesting essential roles of these cellular proteins in viral DNA replication. The discovery of Topo I and II as enzymes indispensable for KSHV DNA replication raises a possibility that these cellular proteins could be new targets of therapeutic approaches to halt KSHV replication and treat KSHV-associated diseases. In this report, we examined one Topo I inhibitor and several Topo II inhibitors (inclusive of Topo II poison and catalytic inhibitors) as potential therapeutic agents for blocking KSHV replication. The Topo II catalytic inhibitors in general exhibited marked inhibition on KSHV replication and minimal cytotoxicity. In particular, novobiocin, with the best selectivity index (SI = 31.62) among the inhibitors tested in this study, is effective in inhibiting KSHV DNA replication and virion production but shows little adverse effect on cell proliferation and cycle progression in its therapeutic concentration, suggesting its potential to become an effective and safe drug for the treatment of human diseases associated with KSHV infection.

scholarly journals Principal Role of TRAP/Mediator and SWI/SNF Complexes in Kaposi's Sarcoma-Associated Herpesvirus RTA-Mediated Lytic Reactivation

2003 ◽  
Vol 23 (6) ◽  
pp. 2055-2067 ◽  
Author(s):  
Yousang Gwack ◽  
Hwa Jin Baek ◽  
Hiroyuki Nakamura ◽  
Sun Hwa Lee ◽  
Michael Meisterernst ◽  
...  
Keyword(s):  
Gene Expression ◽  
Kaposi's Sarcoma ◽  
Viral Gene Expression ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Viral Gene ◽  
Transcription Activator ◽  
Lytic Reactivation ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT An important step in the herpesvirus life cycle is the switch from latency to lytic reactivation. The RTA transcription activator of Kaposi's sarcoma-associated herpesvirus (KSHV) acts as a molecular switch for lytic reactivation. Here we demonstrate that KSHV RTA recruits CBP, the SWI/SNF chromatin remodeling complex, and the TRAP/Mediator coactivator into viral promoters through interactions with a short acidic sequence in the carboxyl region and that this recruitment is essential for RTA-dependent viral gene expression. The Brg1 subunit of SWI/SNF and the TRAP230 subunit of TRAP/Mediator were shown to interact directly with RTA. Consequently, genetic ablation of these interactions abolished KSHV lytic replication. These results demonstrate that the recruitment of CBP, SWI/SNF, and TRAP/Mediator complexes by RTA is the principal mechanism to direct well-controlled viral gene expression and thereby viral lytic reactivation.

scholarly journals Activation of CD21 and CD23 Gene Expression by Kaposi's Sarcoma-Associated Herpesvirus RTA

2005 ◽  
Vol 79 (8) ◽  
pp. 4651-4663 ◽  
Author(s):  
Heesoon Chang ◽  
Yousang Gwack ◽  
Dior Kingston ◽  
John Souvlis ◽  
Xiaozhen Liang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Kaposi's Sarcoma ◽  
Core Promoter ◽  
Human Lymphocytes ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Transcription Activator ◽  
Activation Markers ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Epstein-Barr virus (EBV) EBNA2 and Kaposi's sarcoma-associated herpesvirus (KSHV) replication and transcription activator (RTA) are recruited to their responsive elements through interaction with a Notch-mediated transcription factor, RBP-Jκ. In particular, RTA and EBNA2 interactions with RBP-Jκ are essential for the lytic replication of KSHV and expression of B-cell activation markers CD21 and CD23a, respectively. Here, we demonstrate that like EBV EBNA2, KSHV RTA strongly induces CD21 and CD23a expression through RBP-Jκ binding sites in the first intron of CD21 and in the CD23a core promoter, respectively. However, unlike EBV EBNA2, which alters immunoglobulin μ (Igμ) and c-myc gene expression, RTA did not affect Igμ and c-myc expression, indicating that KSHV RTA targets the Notch signal transduction pathway in a manner similar to but distinct from that of EBV EBNA2. Furthermore, RTA-induced expression of CD21 glycoprotein, which is an EBV receptor, efficiently facilitated EBV infection. In addition, RTA-induced CD23 glycoprotein underwent proteolysis and gave rise to soluble CD23 (sCD23) molecules in B lymphocytes and KSHV-infected primary effusion lymphocytes. sCD23 then stimulated primary human lymphocytes. These results demonstrate that cellular CD21 and CD23a are common targets for B lymphotropic gammaherpesviruses and that KSHV RTA regulates RBP-Jκ-mediated cellular gene expression, which ultimately provides a favorable milieu for viral reproduction in the infected host.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus Utilizes and Manipulates RNA N6-Adenosine Methylation To Promote Lytic Replication

2017 ◽  
Vol 91 (16) ◽  
Author(s):  
Fengchun Ye ◽  
E. Ricky Chen ◽  
Timothy W. Nilsen
Keyword(s):  
Mammalian Cells ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Mrna Splicing ◽  
Rna Modification ◽  
Transcription Activator ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
First Time

ABSTRACT N6-adenosine methylation (m6A) is the most common posttranscriptional RNA modification in mammalian cells. We found that most transcripts encoded by the Kaposi's sarcoma-associated herpesvirus (KSHV) genome undergo m6A modification. The levels of m6A-modified mRNAs increased substantially upon stimulation for lytic replication. The blockage of m6A inhibited splicing of the pre-mRNA encoding the replication transcription activator (RTA), a key KSHV lytic switch protein, and halted viral lytic replication. We identified several m6A sites in RTA pre-mRNA crucial for splicing through interactions with YTH domain containing 1 (YTHDC1), an m6A nuclear reader protein, in conjunction with serine/arginine-rich splicing factor 3 (SRSF3) and SRSF10. Interestingly, RTA induced m6A and enhanced its own pre-mRNA splicing. Our results not only demonstrate an essential role of m6A in regulating RTA pre-mRNA splicing but also suggest that KSHV has evolved a mechanism to manipulate the host m6A machinery to its advantage in promoting lytic replication. IMPORTANCE KSHV productive lytic replication plays a pivotal role in the initiation and progression of Kaposi's sarcoma tumors. Previous studies suggested that the KSHV switch from latency to lytic replication is primarily controlled at the chromatin level through histone and DNA modifications. The present work reports for the first time that KSHV genome-encoded mRNAs undergo m6A modification, which represents a new mechanism at the posttranscriptional level in the control of viral replication.

scholarly journals Kv1.3 induced hyperpolarisation and Cav3.2-mediated calcium entry are required for efficient Kaposi’s sarcoma-associated herpesvirus lytic replication

2021 ◽  
Author(s):  
Holli Carden ◽  
Mark L. Dallas ◽  
David J. Hughes ◽  
Jonathan D. Lippiat ◽  
Jamel Mankouri ◽  
...  
Keyword(s):  
B Cell ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Host Factors ◽  
Transcription Activator ◽  
Intracellular Ca ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
First Time

AbstractUnderstanding the host factors critical for Kaposi’s sarcoma-associated herpesvirus (KSHV) lytic replication can identify new targets for therapeutic intervention. Using pharmacological and genetic silencing approaches, we reveal for the first time that KSHV requires a B cell expressed voltage-gated K+ channel, Kv1.3, to enhance lytic replication. We show that the KSHV replication and transcription activator (RTA) protein upregulates Kv1.3 expression, leading to enhanced K+ channel activity and hyperpolarisation of the B cell membrane. Enhanced Kv1.3 activity then promotes intracellular Ca2+ influx through Cav3.2, a T-type Ca2+ channel, leading to the Ca2+ driven nuclear localisation of NFAT and the subsequent NFAT1-responsive gene expression. Importantly, KSHV lytic replication and infectious virion production could be inhibited by both Kv1.3 and Cav3.2 blockers or through Kv1.3 silencing. These findings provide new mechanistic insight into the essential role of host ion channels during KSHV infection and highlight Kv1.3 and Cav3.2 as new druggable host factors that are key to the successful completion of KSHV lytic replication.

scholarly journals Activation of the Kaposi's Sarcoma-Associated Herpesvirus Major Latency Locus by the Lytic Switch Protein RTA (ORF50)

2005 ◽  
Vol 79 (13) ◽  
pp. 8493-8505 ◽  
Author(s):  
Satoko Matsumura ◽  
Yuriko Fujita ◽  
Evan Gomez ◽  
Naoko Tanese ◽  
Angus C. Wilson
Keyword(s):  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Early Gene ◽  
Viral Gene ◽  
Transcription Activator ◽  
Potent Inducer ◽  
Alternative Mrna Splicing ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) maintains a latent infection in primary effusion lymphoma cells but can be induced to enter full lytic replication by exposure to a variety of chemical inducing agents or by expression of the KSHV-encoded replication and transcription activator (RTA) protein. During latency, only a few viral genes are expressed, and these include the three genes of the so-called latency transcript (LT) cluster: v-FLIP (open reading frame 71 [ORF71]), v-cyclin (ORF72), and latency-associated nuclear antigen (ORF73). During latency, all three open reading frames are transcribed from a common promoter as part of a multicistronic mRNA. Subsequent alternative mRNA splicing and internal ribosome entry allows for the expression of each protein. Here, we show that transcription of LT cassette mRNA can be induced by RTA through the activation of a second promoter (LTi) immediately downstream of the constitutively active promoter (LTc). We identified a minimal cis-regulatory region, which overlaps with the promoter for the bicistronic K14/v-GPCR delayed early gene that is transcribed in the opposite direction. In addition to a TATA box at −30 relative to the LTi mRNA start sites, we identified three separate RTA response elements that are also utilized by the K14/v-GPCR promoter. Interestingly, LTi is unresponsive to sodium butyrate, a potent inducer of lytic replication. This suggests there is a previously unrecognized class of RTA-responsive promoters that respond to direct, but not indirect, induction of RTA. These studies highlight the fact that induction method can influence the precise program of viral gene expression during early events in reactivation and also suggest a mechanism by which RTA contributes to establishment of latency during de novo infections.

scholarly journals Identification and characterization of a new Kaposi's sarcoma-associated herpesvirus replication and transcription activator (RTA)-responsive element involved in RTA-mediated transactivation

2009 ◽  
Vol 90 (4) ◽  
pp. 944-953 ◽  
Author(s):  
Hui-Ju Wen ◽  
Veenu Minhas ◽  
Charles Wood
Keyword(s):  
Transcriptional Activation ◽  
Kaposi's Sarcoma ◽  
Consensus Sequence ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Gene Promoters ◽  
Transcription Activator ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Responsive Element ◽  
Kaposi’S Sarcoma Associated Herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) replication and transcription activator (RTA) is well established as a key transcriptional activator that regulates the KSHV life cycle from latency to lytic replication. It is expressed immediately after infection and activates a number of viral genes leading to virus replication. The RTA-responsive element (RRE) in the RTA target gene promoters is critical for RTA to mediate this transactivation. A number of non-conserved RREs have been identified in various RTA-responsive promoters, and AT-rich sequences have been proposed to serve as RTA targets, but no consensus RRE sequence has been identified so far. Two non-conserved RREs (RRE1 and RRE2) containing AT-rich sequences have been identified previously in the promoter of one of the KSHV lytic genes, ORF57, which can be strongly activated by RTA. Based on homology with the consensus sequence of the Epstein–Barr virus Rta RRE, this study identified a third RTA-responsive element (RRE3) in the ORF57 promoter. This RRE comprised a GC-rich sequence that could bind RTA both in vitro and in vivo, and plays a role in RTA-mediated transactivation of the ORF57 promoter. The presence of two of the three RREs in close proximity to each other was required for optimal RTA-mediated transactivation of the ORF57 promoter, even though the presence of only one RRE is needed for RTA binding. These results suggest that the ability of RTA to mediate transcriptional activation is distinct from its ability to bind to its target elements.

scholarly journals Requirement of a 12-Base-Pair TATT-Containing Sequence and Viral Lytic DNA Replication in Activation of the Kaposi's Sarcoma-Associated Herpesvirus K8.1 Late Promoter

2004 ◽  
Vol 78 (5) ◽  
pp. 2609-2614 ◽  
Author(s):  
Shuang Tang ◽  
Koji Yamanegi ◽  
Zhi-Ming Zheng
Keyword(s):  
Dna Replication ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Late Promoter ◽  
Viral Dna Replication ◽  
Origin Of Dna Replication ◽  
Infected Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Lytic Dna Replication

ABSTRACT Kaposi's sarcoma-associated herpesvirus (KSHV) K8.1 late promoter consists of a minimal 24-bp sequence, with a TATA-like, 12-bp promoter core, AATATTAAAGGG, and is active on a reporter only in butyrate-induced KSHV-infected cells. The activity of the K8.1 promoter can be enhanced (>15-fold) by the KSHV left-end lytic origin of DNA replication (oriLyt-L) sequence while providing inefficient replication of plasmid DNA and is inhibited by viral DNA replication inhibitors, suggesting that activation of the K8.1 promoter on the reporter is involved in KSHV lytic DNA replication largely by trans.

scholarly journals Cellular Corepressor TLE2 Inhibits Replication-and-Transcription- Activator-Mediated Transactivation and Lytic Reactivation of Kaposi's Sarcoma-Associated Herpesvirus

2009 ◽  
Vol 84 (4) ◽  
pp. 2047-2062 ◽  
Author(s):  
Zhiheng He ◽  
Yunhua Liu ◽  
Deguang Liang ◽  
Zhuo Wang ◽  
Erle S. Robertson ◽  
...  
Keyword(s):  
Kaposi's Sarcoma ◽  
Binding Protein ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Host Protein ◽  
Transcription Activator ◽  
Rich Domain ◽  
Lytic Reactivation ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Replication and transcription activator (RTA) encoded by open reading frame 50 (ORF50) of Kaposi's sarcoma-associated herpesvirus (KSHV) is essential and sufficient to initiate lytic reactivation. RTA activates its target genes through direct binding with high affinity to its responsive elements or by interaction with cellular factors, such as RBP-Jκ, Ap-1, C/EBP-α, and Oct-1. In this study, we identified transducin-like enhancer of split 2 (TLE2) as a novel RTA binding protein by using yeast two-hybrid screening of a human spleen cDNA library. The interaction between TLE2 and RTA was confirmed by glutathione S-transferase (GST) binding and coimmunoprecipitation assays. Immunofluorescence analysis showed that TLE2 and RTA were colocalized in the same nuclear compartment in KSHV-infected cells. This interaction recruited TLE2 to RTA bound to its recognition sites on DNA and repressed RTA auto-activation and transactivation activity. Moreover, TLE2 also inhibited the induction of lytic replication and virion production driven by RTA. We further showed that the Q (Gln-rich), SP (Ser-Pro-rich), and WDR (Trp-Asp repeat) domains of TLE2 and the Pro-rich domain of RTA were essential for this interaction. RBP-Jκ has been shown previously to bind to the same Pro-rich domain of RTA, and this binding can be subject to competition by TLE2. In addition, TLE2 can form a complex with RTA to access the cognate DNA sequence of the RTA-responsive element at different promoters. Intriguingly, the transcription level of TLE2 could be upregulated by RTA during the lytic reactivation process. In conclusion, we identified a new RTA binding protein, TLE2, and demonstrated that TLE2 inhibited replication and transactivation mediated by RTA. This provides another potentially important mechanism for maintenance of KSHV viral latency through interaction with a host protein.

scholarly journals Enhancement of Autophagy during Lytic Replication by the Kaposi's Sarcoma-Associated Herpesvirus Replication and Transcription Activator

2010 ◽  
Vol 84 (15) ◽  
pp. 7448-7458 ◽  
Author(s):  
Hui-Ju Wen ◽  
Zhilong Yang ◽  
You Zhou ◽  
Charles Wood
Keyword(s):  
Kaposi's Sarcoma ◽  
Degradation Mechanism ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Transcription Activator ◽  
Lytic Gene ◽  
Lytic Reactivation ◽  
Autophagic Process ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Autophagy is one of two major degradation systems in eukaryotic cells. The degradation mechanism of autophagy is required to maintain the balance between the biosynthetic and catabolic processes and also contributes to defense against invading pathogens. Recent studies suggest that a number of viruses can evade or subvert the host cell autophagic pathway to enhance their own replication. Here, we investigated the effect of autophagy on the KSHV (Kaposi's sarcoma-associated herpesvirus) life cycle. We found that the inhibition of autophagy reduces KSHV lytic reactivation from latency, and an enhancement of autophagy can be detected during KSHV lytic replication. In addition, RTA (replication and transcription activator), an essential viral protein for KSHV lytic reactivation, is able to enhance the autophagic process, leading to an increase in the number of autophagic vacuoles, an increase in the level of the lipidated LC3 protein, and the formation of autolysosomes. Moreover, the inhibition of autophagy affects RTA-mediated lytic gene expression and viral DNA replication. These results suggest that RTA increases autophagy activation to facilitate KSHV lytic replication. This is the first report demonstrating that autophagy is involved in the lytic reactivation of KSHV.

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