scholarly journals Kaposi's Sarcoma-Associated Herpesvirus Transactivator Rta Induces Cell Cycle Arrest in G0/G1 Phase by Stabilizing and Promoting Nuclear Localization of p27kip

2013 ◽  
Vol 87 (24) ◽  
pp. 13226-13238 ◽  
Author(s):  
P. Kumar ◽  
C. Wood
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Nuclear Localization ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
G1 Phase ◽  
Cycle Arrest ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus MicroRNAs Target GADD45B To Protect Infected Cells from Cell Cycle Arrest and Apoptosis

2016 ◽  
Vol 91 (3) ◽  
Author(s):  
Xiaoyan Liu ◽  
Christine Happel ◽  
Joseph M. Ziegelbauer
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Arrest ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Cycle Arrest ◽  
Damage Response ◽  
Infected Cells ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Kaposi's sarcoma is one of the most common malignancies in HIV-infected individuals. The responsible agent, Kaposi's sarcoma-associated herpesvirus (KSHV; HHV8), expresses multiple microRNAs (miRNAs), but the targets and functions of these miRNAs are not completely understood. After infection in primary endothelial cells with KSHV, growth arrest DNA damage-inducible gene 45 beta (GADD45B) is one of the most repressed genes using genomic expression profiling. GADD45B was also repressed in mRNA expression profiling experiments when KSHV miRNAs were introduced to uninfected cells. We hypothesized that KSHV miRNAs target human GADD45B to protect cells from consequences of DNA damage, which can be triggered by viral infection. Expression of GADD45B protein is induced by the p53 activator, Nutlin-3, and KSHV miRNA-K9 inhibits this induction. In addition, Nutlin-3 increased apoptosis and cell cycle arrest based on flow cytometry assays. KSHV miR-K9 protected primary endothelial cells from apoptosis and cell cycle arrest following Nutlin-3 treatment. Similar protective phenotypes were seen for targeting GADD45B with short interfering RNAs (siRNAs), as with miR-K9. KSHV miR-K9 also decreased the protein levels of cleaved caspase-3, cleaved caspase-7, and cleaved poly(ADP-ribose) polymerase (PARP). In B lymphocytes latently infected with KSHV, specific inhibitors of KSHV miR-K9 led to increased GADD45B expression and apoptosis, indicating that miR-K9 is important for reducing apoptosis in infected cells. Furthermore, ectopic expression of GADD45B in KSHV-infected cells promoted apoptosis. Together, these results identify a new miRNA target and demonstrate that KSHV miRNAs are important for protecting infected cells from DNA damage responses. IMPORTANCE Kaposi's sarcoma-associated herpesvirus is a leading cause of cancers in individuals with AIDS. Promoting survival of infected cells is essential for maintaining viral infections. A virus needs to combat various cellular defense mechanisms designed to eradicate the viral infection. One such response can include DNA damage response factors, which can promote an arrest in cell growth and trigger cell death. We used a new approach to search for human genes repressed by small nucleic acids (microRNAs) expressed by a gammaherpesvirus (KSHV), which identified a gene called GADD45B as a target of microRNAs. Repression of GADD45B, which is expressed in response to DNA damage, benefited survival of infected cells in response to a DNA damage response. This information could be used to design new treatments for herpesvirus infections.

scholarly journals Characterization and Cell Cycle Regulation of the Major Kaposi’s Sarcoma-Associated Herpesvirus (Human Herpesvirus 8) Latent Genes and Their Promoter

1999 ◽  
Vol 73 (2) ◽  
pp. 1438-1446 ◽  
Author(s):  
Ronit Sarid ◽  
Jeffrey S. Wiezorek ◽  
Patrick S. Moore ◽  
Yuan Chang
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Cell Cycle Regulation ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Mrna Levels ◽  
Cycle Arrest ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Cycle Regulation

ABSTRACT Retinoblastoma tumor suppressor protein (pRB) inhibition by tumor virus oncoproteins has been attributed to the need for these viruses to promote lytic viral nucleic acid synthesis by unscheduled entry into the S phase of the cell cycle. Kaposi’s sarcoma-associated herpesvirus (KSHV or HHV8) encodes a functional cyclin (vCYC) which is expressed during latency and can direct phosphorylation of pRB. We mapped the two major latent transcripts encoding vCYC, latent transcript 1 (LT1) and LT2, by cDNA sequencing, 5′ rapid amplification of cDNA ends, and primer extension analyses. Both LT1 and LT2 transcripts are spliced, originate from the same start site, and encode ORF K13 (vFLIP) as well as ORF72 (vCYC). The latency-associated nuclear antigen (LANA, ORF73) is encoded by LT1 but spliced from LT2. While differential expression of the two transcripts was not found, the promoter controlling LT1/LT2 transcription is regulated in a cell cycle-dependent manner. Activities of both KSHV LT1/LT2 and huCYC D1 luciferase promoter reporters transfected into NIH 3T3 cells increase 11- and 4-fold, respectively, after release from cell cycle arrest by serum starvation. Further, vCYC and huCYC D2 mRNA levels are low in naturally infected BCBL-1 cells arrested in late G1 with l-mimosine but increase in parallel during a 24-h period after release from cell cycle arrest. Cell cycle regulation of KSHV vCYC expression mimics cellular D cyclin regulation and may maintain infected cell cycling. This is consistent with an alternative hypothesis that tumor viruses have developed specific responses to innate cellular defenses against latent virus infection that include pRB-induced cell cycle arrest.

scholarly journals Myc Is Required for the Maintenance of Kaposi's Sarcoma-Associated Herpesvirus Latency

2010 ◽  
Vol 84 (17) ◽  
pp. 8945-8948 ◽  
Author(s):  
Xudong Li ◽  
Shijia Chen ◽  
Jun Feng ◽  
Hongyu Deng ◽  
Ren Sun
Keyword(s):  
Cell Cycle ◽  
Kaposi's Sarcoma ◽  
Promoter Activity ◽  
Primary Effusion Lymphoma ◽  
Kaposi’S Sarcoma ◽  
Cellular Transformation ◽  
Mrna Levels ◽  
Cycle Arrest ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Myc is deregulated by Kaposi's sarcoma-associated herpesvirus (KSHV) latent proteins, but its role in KSHV latency is not clear. We found that Myc knockdown with RNA interference (RNAi) induced KSHV reactivation and increased the protein and mRNA levels of RTA, a key viral regulator of KSHV reactivation. Myc knockdown increased, whereas Myc overexpression inhibited, RTA promoter activity. KSHV reactivation and the activation of the RTA promoter induced by Myc depletion were inhibited by c-Jun N-terminal kinase (JNK) and p38 inhibitors but not by a MEK1 inhibitor. Myc knockdown inhibited primary effusion lymphoma (PEL) cell proliferation through inducing apoptosis and G1 cell cycle arrest. Thus, Myc may be a key cellular node coupling cellular transformation and KSHV latency.

scholarly journals Identification of the Nuclear Export and Adjacent Nuclear Localization Signals for ORF45 of Kaposi's Sarcoma-Associated Herpesvirus

2008 ◽  
Vol 83 (6) ◽  
pp. 2531-2539 ◽  
Author(s):  
Xiaojuan Li ◽  
Fanxiu Zhu
Keyword(s):  
Subcellular Localization ◽  
Nuclear Localization ◽  
Nuclear Export ◽  
Kaposi's Sarcoma ◽  
Nuclear Export Signal ◽  
Kaposi’S Sarcoma ◽  
Lytic Replication ◽  
Wild Type ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

ABSTRACT Open reading frame 45 (ORF45) of Kaposi's sarcoma-associated herpesvirus 8 (KSHV) is an immediate-early phosphorylated tegument protein and has been shown to play important roles at both early and late stages of viral infection. Homologues of ORF45 exist only in gammaherpesviruses, and their homology is limited. These homologues differ in their protein lengths and subcellular localizations. We and others have reported that KSHV ORF45 is localized predominantly in the cytoplasm, whereas its homologue in murine herpesvirus 68 is localized exclusively in the nucleus. We observed that ORF45s of rhesus rhadinovirus and herpesvirus saimiri are found exclusively in the nucleus. As a first step toward understanding the mechanism underlying the distinct intracellular distribution of KSHV ORF45, we identified the signals that control its subcellular localization. We found that KSHV ORF45 accumulated rapidly in the nucleus in the presence of leptomycin B, an inhibitor of CRM1 (exportin 1)-dependent nuclear export, suggesting that it could shuttle between the nucleus and cytoplasm. Mutational analysis revealed that KSHV ORF45 contains a CRM1-dependent, leucine-rich-like nuclear export signal and an adjacent nuclear localization signal. Replacement of the key residues with alanines in these motifs of ORF45 disrupts its shuttling between the cytoplasm and nucleus. The resulting ORF45 mutants have restricted subcellular localizations, being found exclusively either in the cytoplasm or in the nucleus. Recombinant viruses were reconstituted by introduction of these mutations into KSHV bacterial artificial chromosome BAC36. The resultant viruses have distinct phenotypes. A mutant virus in which ORF45 is restricted to the cytoplasm behaves as an ORF45-null mutant and produces 5- to 10-fold fewer progeny viruses than the wild type. In contrast, mutants in which the ORF45 protein is mostly restricted to the nucleus produce numbers of progeny viruses similar to those produced by the wild type. These data suggest that the subcellular localization signals of ORF45 have important functional roles in KSHV lytic replication.

scholarly journals Identification of a Novel Cellular Transcriptional Repressor Interacting with the Latent Nuclear Antigen of Kaposi's Sarcoma-Associated Herpesvirus

2003 ◽  
Vol 77 (18) ◽  
pp. 9758-9768 ◽  
Author(s):  
Hong-Yi Pan ◽  
Yan-Jin Zhang ◽  
Xin-Ping Wang ◽  
Jian-Hong Deng ◽  
Fu-Chun Zhou ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Kaposi's Sarcoma ◽  
Promoter Activity ◽  
Kaposi’S Sarcoma ◽  
Nuclear Antigen ◽  
Northern Blot Hybridization ◽  
Nuclear Localization Signals ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Latent Nuclear Antigen

ABSTRACT The latent nuclear antigen (LNA) of Kaposi's sarcoma-associated herpesvirus (KSHV) has an essential role in viral latent infection. LNA maintains the stability of KSHV episomes and modulates the expression of cellular genes. A novel cellular protein KLIP1 was identified to interact with LNA through yeast two-hybrid screening, and confirmed by a glutathione S-transferase pull down assay. Domain mapping showed that KLIP1 interacted with the N-terminal domain of LNA. Northern blot hybridization with a KLIP1 probe identified a major transcript of 1.8 kb and a minor transcript of 2.8 kb. cDNA library screening and 5′-RACE revealed that the major transcript encoded an open-reading-frame of 1,257 bp and had a 5′-untranslated region of 73 nucleotides. The major KLIP1 transcript was ubiquitously present in different cell types examined. A KLIP1 synthetic peptide antibody detected a doublet of 58-kDa and 63-kDa proteins in a Western blot assay. KLIP1 had two putative nuclear localization signals and showed punctate nuclear localization when expressed as a GFP-fusion protein. KLIP1 interacted with LNA in vivo, as demonstrated by coimmunoprecipitation using KSHV-infected cells and colocalization when they were expressed as GFP- and DsRed-fusion proteins, respectively. Consistent with its interaction with LNA, nuclear localization, and possession of two leucine zipper motifs, KLIP1 behaved like a transcriptional factor and repressed herpes simplex virus thymidine kinase (TK) promoter activity in a mammalian one-hybrid assay. In addition, cotransfection with LNA alleviated the transcriptional repression effect of KLIP1 on TK promoter activity. These results suggest that KLIP1 is a new member of cellular transcriptional repressors, and that LNA is involved in deregulating cellular transcription process.

scholarly journals Kaposi's Sarcoma-Associated Herpesvirus Viral Interferon Regulatory Factor 4 (vIRF4) Perturbs the G1-S Cell Cycle Progression via Deregulation of thecyclin D1Gene

2015 ◽  
Vol 90 (2) ◽  
pp. 1139-1143 ◽  
Author(s):  
Hye-Ra Lee ◽  
Jaba Mitra ◽  
Stacy Lee ◽  
Shou-Jiang Gao ◽  
Tae-Kwang Oh ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Kaposi's Sarcoma ◽  
Cell Cycle Progression ◽  
Kaposi’S Sarcoma ◽  
Regulatory Factor ◽  
Cycle Progression ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Interferon Regulatory Factor 4 ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
Intracellular Milieu

Kaposi's sarcoma-associated herpesvirus (KSHV) infection modulates the host cell cycle to create an environment optimal for its viral-DNA replication during the lytic life cycle. We report here that KSHV vIRF4 targets the β-catenin/CBP cofactor and blocks its occupancy on thecyclin D1promoter, suppressing the G1-S cell cycle progression and enhancing KSHV replication. This shows that KSHV vIRF4 suppresses host G1-S transition, possibly providing an intracellular milieu favorable for its replication.

scholarly journals Identifying cellular genes crucial for the reactivation of Kaposi's sarcoma-associated herpesvirus latency

2006 ◽  
Vol 87 (3) ◽  
pp. 519-529 ◽  
Author(s):  
Benjaman A. Bryan ◽  
Ossie F. Dyson ◽  
Shaw M. Akula
Keyword(s):  
Cell Cycle ◽  
Flow Cytometry ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
S Phase ◽  
Lytic Cycle ◽  
Kshv Infection ◽  
Cellular Genes ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) is the latest addition to the long list of human herpesviruses. Reactivation of latent herpesvirus infections is still a mystery. It was demonstrated recently that the phorbol ester TPA was efficient in inducing a reactivation of KSHV infection in the S phase of the cell cycle. In the present study, flow cytometry-sorted, TPA-induced, KSHV-infected haematopoietic cells (BCBL-1) were used to analyse the expression profiles of cancer-related cellular genes in the S phase of the cell cycle compared with the G0/1 phase by using microarrays. Overall, the S phase of the cell cycle seems to provide KSHV with an apt environment for a productive lytic cycle of infection. The apt conditions include cellular signalling that promotes survivability, DNA replication and lipid metabolism, while blocking cell-cycle progression to M phase. Some of the important genes that were overexpressed during the S phase of the cell cycle compared with the G0/1 phase of TPA-induced BCBL-1 cells are v-myb myeloblastosis (MYBL2), protein kinase-membrane associated tyrosine/threonine 1 (PKMYT1), ribonucleotide reductase M1 polypeptide (RRM1) and peroxisome proliferator-activated receptors delta (PPARD). Inhibition of PKMYT1 expression by the use of specific short interfering RNAs significantly lowered the TPA-induced KSHV lytic cycle of infection. The significance of these and other genes in the reactivation of KSHV is discussed in the following report. Taken together, a flow cytometry–microarray-based method to study the cellular conditions critical for the reactivation of KSHV infection is reported here for the first time.

scholarly journals ORF73 of Herpesvirus Saimiri, a Viral Homolog of Kaposi's Sarcoma-Associated Herpesvirus, Modulates the Two Cellular Tumor Suppressor Proteins p53 and pRb

2004 ◽  
Vol 78 (19) ◽  
pp. 10336-10347 ◽  
Author(s):  
Sumit Borah ◽  
Subhash C. Verma ◽  
Erle S. Robertson
Keyword(s):  
Cell Cycle ◽  
Kaposi's Sarcoma ◽  
Kaposi’S Sarcoma ◽  
Herpesvirus Saimiri ◽  
Nuclear Antigen ◽  
Kaposi's Sarcoma Associated Herpesvirus ◽  
Kaposi’S Sarcoma Associated Herpesvirus ◽  
P53 Inactivation

ABSTRACT All known DNA tumor viruses are known to target and inactivate two main cell cycle regulatory proteins, retinoblastoma protein (pRb) and p53. Inactivation of pRb promotes host cell cycle progression into S phase, and inactivation of p53 promotes cell immortalization. The DNA tumor virus Kaposi's sarcoma associated herpesvirus (KSHV)-encoded latency-associated nuclear antigen (LANA) was shown to target and inactivate pRb as well as p53. In this report we provide evidence that these functions are conserved in the homologous protein encoded by the related gammaherpesvirus herpesvirus saimiri (HVS). ORF73, the HVS homologue of LANA, is shown to bind both p53 and pRb in vitro and in vivo, to colocalize with p53 in human T cells infected with HVS, and in cells overexpressing both ORF73 and p53, as well as to adversely influence pRB/E2F and p53 transcriptional regulation. The C terminus of LANA, the region most highly conserved in ORF73, is shown to be responsible for both pRb and p53 interactions, supporting the hypothesis that these functions are conserved in both homologues. Finally, the region of p53 targeted by LANA (and ORF73) maps to the domain required for tetramerization. However, preliminary cross-linking studies do not detect disruption of p53 tetramerization by either LANA or HVS-encoded ORF73, suggesting that p53 inactivation may be by a mechanism independent of tetramer disruption.

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