Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The etiology and pathogenesis of Hodgkin lymphoma (HL) are not yet known. There are implications of genes involved in programmed cell death (apoptosis), and there have been repeated suggestions of an association with Epstein-Barr virus (EBV). The aim of this study was to investigate the protein expression patterns of key cell cycle-related genes, together with evidence of apoptosis and EBV status, in relation to clinical stage in HLs. A double immunohistochemical and in situ hybridization technique was used to detect the expression of bcl-2, p53, retinoblastoma (Rb), p21, Ki67 (MIB 1), and topoisomerase IIalpha (TopoIIalpha), together with latent membrane protein-1 and EBER for EBV status and TdT-mediated dUTP-FITC nick end-labeling (TUNEL) as a measure of apoptosis, on tissue microarray sections of 62 cases of classic HL (35 NS, 17 MC, 8 LR, and 2 LD). A panel of phenotypic markers was used to facilitate recognition of Hodgkin and Reed-Sternberg (H-RS) cells: CD3, CD20, CD30, CD15, and EMA. The H-RS cells of 62 classic Hodgkin lymphomas were bcl-2-positive in 35 cases (56.45%), p53-positive in 14 (22.58%), and positive for both EBV latent membrane protein-1 and EBER in 37 (59.68%); there was complete concordance of results for EBV by both procedures. No correlation was found between expression of bcl-2, p53, or EBV markers in H-RS cells and clinical stage (P > 0.05). Expression of Rb, Ki67, p21, and TopoIIalpha did, however, show significant differences with clinical stage. Expression of Rb and p21 in CD30-positive H-RS cells decreased with more advanced stage (P < 0.001). In contrast, Ki67 and ToPoIIalpha expression increased with later stage (P < 0.01). No correlation was found between expression of any of these markers in H-RS cells and the subtypes of nodular sclerosis HL, mixed cellularity HL, and LRHL (P > 0.05). TUNEL was found in the nonneoplastic cellular background in all cases and in H-RS cells in only 10 of 62 cases (16.12%) (8 nodular sclerosis HL, 1 mixed cellularity HL, and 1 LRHL). There was a significant correlation between high expression of bcl-2 and a low score by TUNEL (P < 0.05). These data are consistent with the notion that overexpression of bcl-2 may be linked to blockage of apoptosis-mediated death of H-RS cells in classic HL. Abnormal expression of p53-related protein may not play a major role in HL, because it is present in H-RS cells in only a minority of cases. Increased expression of Ki67 and TopoIIalpha by H-RS cells is significantly associated with advanced stage and may indicate aggressive disease. Adverse clinical outcome in HL also is associated with loss of Rb and p21 protein expression, consistent with the possible roles of Rb and p21 in inhibition of the growth of H-RS cells. Within the limitations of the methods used, almost two thirds of cases of HL provide evidence of an association with EBV. The tissue microarray technique is valuable not only for examination of large numbers of cases of a disease by a complex panel of markers but also potentially as a control for staining quality in immunohistochemistry and in situ hybridization.
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PMID:Apoptosis and cell cycle-related genes and proteins in classical Hodgkin lymphoma: application of tissue microarray technique. 1296 46

Previous studies of Epstein-Barr virus (EBV) replication focused mainly on the viral and cellular factors involved in replication compartment assembly and controlling the cell cycle. However, little is known about how EBV reorganizes nuclear architecture and the chromatin territories. In EBV-positive nasopharyngeal carcinoma NA cells or Akata cells, we noticed that cellular chromatin becomes highly condensed upon EBV reactivation. In searching for the possible mechanisms involved, we found that transient expression of EBV BGLF4 kinase induces unscheduled chromosome condensation, nuclear lamina disassembly, and stress fiber rearrangements, independently of cellular DNA replication and Cdc2 activity. BGLF4 interacts with condensin complexes, the major components in mitotic chromosome assembly, and induces condensin phosphorylation at Cdc2 consensus motifs. BGLF4 also stimulates the decatenation activity of topoisomerase II, suggesting that it may induce chromosome condensation through condensin and topoisomerase II activation. The ability to induce chromosome condensation is conserved in another gammaherpesvirus kinase, murine herpesvirus 68 ORF36. Together, these findings suggest a novel mechanism by which gammaherpesvirus kinases may induce multiple premature mitotic events to provide more extrachromosomal space for viral DNA replication and successful egress of nucleocapsid from the nucleus.
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PMID:Epstein-Barr virus BGLF4 kinase induces premature chromosome condensation through activation of condensin and topoisomerase II. 1736 Jul 54

DNA viruses adopt various strategies to modulate the cellular environment for efficient genome replication and virion production. Previously, we demonstrated that the BGLF4 kinase of Epstein-Barr virus (EBV) induces premature chromosome condensation through the activation of condensin and topoisomerase IIalpha (C. P. Lee, J. Y. Chen, J. T. Wang, K. Kimura, A. Takemoto, C. C. Lu, and M. R. Chen, J. Virol. 81:5166-5180, 2007). In this study, we show that BGLF4 interacts with lamin A/C and phosphorylates lamin A protein in vitro. Using a green fluorescent protein (GFP)-lamin A system, we found that Ser-22, Ser-390, and Ser-392 of lamin A are important for the BGLF4-induced disassembly of the nuclear lamina and the EBV reactivation-mediated redistribution of nuclear lamin. Virion production and protein levels of two EBV primary envelope proteins, BFRF1 and BFLF2, were reduced significantly by the expression of GFP-lamin A(5A), which has five Ser residues replaced by Ala at amino acids 22, 390, 392, 652, and 657 of lamin A. Our data indicate that BGLF4 kinase phosphorylates lamin A/C to promote the reorganization of the nuclear lamina, which then may facilitate the interaction of BFRF1 and BFLF2s and subsequent virion maturation. UL kinases of alpha- and betaherpesviruses also induce the disassembly of the nuclear lamina through similar sites on lamin A/C, suggesting a conserved mechanism for the nuclear egress of herpesviruses.
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PMID:Epstein-Barr virus BGLF4 kinase induces disassembly of the nuclear lamina to facilitate virion production. 1881 3

The outcome of classical Hodgkin lymphoma (cHL) patients may be related to the tumor microenvironment, which in turn may be influenced by Epstein-Barr virus (EBV) infection. To characterize the cHL microenvironment, a set of 63 cHL tissue samples was profiled using DNA microarrays. Their gene expression profile differed from that of histiocyte T cell-rich B-cell lymphoma (H/TCRBCL) samples that were used as controls, mainly due to high expression of PDCD1/PD-1 in H/TCRBCL. EBV(+) cHL tissues could be distinguished from EBV(-) samples by a gene signature characteristic of Th1 and antiviral responses. Samples from cHL patients with favorable outcome overexpressed genes specific for B cells and genes involved in apoptotic pathways. An independent set of 146 cHL samples was analyzed using immunohistochemistry. It showed a significant adverse value in case of high percentage of either TIA-1(+)-reactive cells or topoisomerase-2(+) tumor cells, whereas high numbers of BCL11A(+), FOXP3(+), or CD20(+) reactive cells had a favorable influence. Our results suggest an antitumoral role for B cells in the cHL microenvironment and a stronger stromal influence of the PD1 pathway in H/TCRBCL than cHL. The observation of Th1/ antiviral response in EBV(+) cHL tissues provides a basis for novel treatment strategies.
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PMID:Molecular profiling of classical Hodgkin lymphoma tissues uncovers variations in the tumor microenvironment and correlations with EBV infection and outcome. 1909 12

Ever since their existence, there has been an everlasting arms race between viruses and their host cells. Host cells have developed numerous strategies to silence viral gene expression whereas viruses always find their ways to overcome these obstacles. Recent studies show that viruses have also evolved to take full advantage of existing cellular chromatin components to activate or repress its own genes when needed. While in most cases viruses encode certain proteins to recruit or inhibit cellular factors through physical interactions, growing examples show that viral-encoded enzymes affect host chromatin structure through post-translationally modifying histones or other cellular proteins important for chromatin function. The most well-studied example is vSET encoded by paramecium bursaria chlorella virus 1. vSET specifically methylates histone H3 at lysine 27, causing genome-wide silencing of Polycomb target genes upon infection, thus mimicking the function of Polycomb repressive complex 2 (PRC2) in eukaryotes. Other examples include BGLF4 from Epstein-Barr virus that affects both condensin and topoisomerase II activity and Us3 from Herpes Simplex virus 1 that inhibits HDAC1 function through phosphorylation.
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PMID:Viral-encoded enzymes that target host chromatin functions. 1971 51

Epstein-Barr virus (EBV) induces an uncoordinated S-phase-like cellular environment coupled with multiple prophase-like events in cells replicating the virus. The EBV encoded Ser/Thr kinase BGLF4 has been shown to induce premature chromosome condensation through activation of condensin and topoisomerase II and reorganization of the nuclear lamina to facilitate the nuclear egress of nucleocapsids in a pathway mimicking Cdk1. However, the observation that RB is hyperphosphorylated in the presence of BGLF4 raised the possibility that BGLF4 may have a Cdk2-like activity to promote S-phase progression. Here, we investigated the regulatory effects of BGLF4 on cell cycle progression and found that S-phase progression and DNA synthesis were interrupted by BGLF4 in mammalian cells. Expression of BGLF4 did not compensate Cdk1 defects for DNA replication in S. cerevisiae. Using time-lapse microscopy, we found the fate of individual HeLa cells was determined by the expression level of BGLF4. In addition to slight cell growth retardation, BGLF4 elicits abnormal chromosomal structure and micronucleus formation in 293 and NCP-TW01 cells. In Saos-2 cells, BGLF4 induced the hyperphosphorylation of co-transfected RB, while E2F1 was not released from RB-E2F1 complexes. The E2F1 regulated activities of the cyclin D1 and ZBRK1 promoters were suppressed by BGLF4 in a dose dependent manner. Detection with phosphoamino acid specific antibodies revealed that, in addition to Ser780, phosphorylation of the DNA damage-responsive Ser612 on RB was enhanced by BGLF4. Taken together, our study indicates that BGLF4 may directly or indirectly induce a DNA damage signal that eventually interferes with host DNA synthesis and delays S-phase progression.
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PMID:Epstein-Barr virus BGLF4 kinase retards cellular S-phase progression and induces chromosomal abnormality. 2276 64

Systemic lupus erythematosus (SLE) is an autoimmune disease that can attack many different body organs; the triggering event is unknown. SLE has been associated with more than 100 different autoantibody reactivities - anti-dsDNA is prominent. Nevertheless, autoantibodies to dsDNA occur in only two-thirds of SLE patients. We previously reported the use of an antigen microarray to characterize SLE serology. We now report the results of an expanded study of serology in SLE patients and scleroderma (SSc) patients compared with healthy controls. The analysis validated and extended previous findings: two-thirds of SLE patients reacted to a large spectrum of self-molecules that overlapped with their reactivity to dsDNA; moreover, some SLE patients manifested a deficiency of natural IgM autoantibodies. Most significant was the finding that many SLE patients who were negative for autoantibodies to dsDNA manifested abnormal antibody responses to Epstein-Barr virus (EBV): these subjects made IgG antibodies to EBV antigens to which healthy subjects did not respond or they failed to make antibodies to EBV antigens to which healthy subjects did respond. This observation suggests that SLE may be associated with a defective immune response to EBV. The SSc patients shared many of these serological abnormalities with SLE patients, but differed from them in increased IgG autoantibodies to topoisomerase and centromere B; 84% of SLE patients and 58% of SSc patients could be detected by their abnormal antibodies to EBV. Hence an aberrant immune response to a ubiquitous viral infection such as EBV might set the stage for an autoimmune disease.
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PMID:Epstein-Barr virus antibodies mark systemic lupus erythematosus and scleroderma patients negative for anti-DNA. 2416

Epstein-Barr virus (EBV) is tightly associated with certain human cancers, but there is as yet no specific treatment against EBV-related diseases. The EBV-encoded EBNA1 protein is essential to maintain viral episomes and for viral persistence. As such, EBNA1 is expressed in all EBV-infected cells, and is highly antigenic. All infected individuals, including individuals with cancer, have CD8(+) T cells directed towards EBNA1 epitopes, yet the immune system fails to detect and destroy cells harboring the virus. EBV immune evasion depends on the capacity of the Gly-Ala repeat (GAr) domain of EBNA1 to inhibit the translation of its own mRNA in cis, thereby limiting the production of EBNA1-derived antigenic peptides presented by the major histocompatibility complex (MHC) class I pathway. Here we establish a yeast-based assay for monitoring GAr-dependent inhibition of translation. Using this assay we identify doxorubicin (DXR) as a compound that specifically interferes with the GAr effect on translation in yeast. DXR targets the topoisomerase-II-DNA complexes and thereby causes genomic damage. We show, however, that the genotoxic effect of DXR and various analogs thereof is uncoupled from the effect on GAr-mediated translation control. This is further supported by the observation that etoposide and teniposide, representing another class of topoisomerase-II-DNA targeting drugs, have no effect on GAr-mediated translation control. DXR and active analogs stimulate, in a GAr-dependent manner, EBNA1 expression in mammalian cells and overcome GAr-dependent restriction of MHC class I antigen presentation. These results validate our approach as an effective high-throughput screening assay to identify drugs that interfere with EBV immune evasion and, thus, constitute candidates for treating EBV-related diseases, in particular EBV-associated cancers.
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PMID:A yeast-based assay identifies drugs that interfere with immune evasion of the Epstein-Barr virus. 2455 96

Improving survival rates in children with malignancy have been achieved at the cost of a high frequency of late adverse effects of treatment, especially in intensively treated patients such as those undergoing haematopoietic stem cell transplantation (HSCT), many of whom suffer the high burden of chronic toxicity. Secondary malignant neoplasms (SMNs) are one of the most devastating late effects, cause much morbidity and are the most frequent cause of late (yet still premature) treatment-related mortality. They occur in up to 7% of HSCT recipients by 20 years post-HSCT, and with no evidence yet of a plateau in incidence with longer follow-up. This review describes the epidemiology, pathogenesis, clinical features and risk factors of the three main categories of post-HSCT SMNs. A wide range of solid SMNs has been described, usually occurring 10 years or more post-HSCT, related most often to previous or conditioning radiotherapy. Therapy-related acute myeloid leukaemia/myelodysplasia occurs earlier, typically three to seven years post-HSCT, mainly in recipients of autologous transplant and is related to previous alkylating agent or topoisomerase II inhibitor chemotherapy. Post-transplant lymphoproliferative disorders occur early (usually within two years) post-HSCT, usually presenting as Epstein-Barr virus-related B cell non-Hodgkin lymphoma.
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PMID:Secondary Malignant Neoplasms Following Haematopoietic Stem Cell Transplantation in Childhood. 2741 56


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