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  • American Society for Microbiology  (6)
  • 1
    Online Resource
    Online Resource
    Human Parvovirus B19 Induces Cell Cycle Arrest at G 2 Phase with Accumulation of Mitotic Cyclins
    American Society for Microbiology ; 2001
    In:  Journal of Virology Vol. 75, No. 16 ( 2001-08-15), p. 7555-7563
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 75, No. 16 ( 2001-08-15), p. 7555-7563
    Abstract: Human parvovirus B19 infects specifically erythroid progenitor cells, which causes transient aplastic crises and hemolytic anemias. Here, we demonstrate that erythroblastoid UT7/Epo cells infected with B19 virus fall into growth arrest with 4N DNA, indicating G 2 /M arrest. These B19 virus-infected cells displayed accumulation of cyclin A, cyclin B1, and phosphorylated cdc2 and were accompanied by an up-regulation in the kinase activity of the cdc2-cyclin B1 complex, similar to that in cells treated with the mitotic inhibitor. However, degradation of nuclear lamina and phosphorylation of histone H3 and H1 were not seen in B19 virus-infected cells, indicating that the infected cells do not enter the M phase. Accumulation of cyclin B1 was persistently localized in the cytoplasm, but not in the nucleus, suggesting that B19 virus infection of erythroid cells raises suppression of nuclear import of cyclin B1, resulting in cell cycle arrest at the G 2 phase. The B19 virus-induced G 2 /M arrest may be the critical event in the damage of erythroid progenitor cells seen in patients with B19 virus infection.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.75.16.7555-7563.2001
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1495529-5
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  • 2
    Online Resource
    Online Resource
    Aberrant Activation of the Interleukin-2 Autocrine Loop through the Nuclear Factor of Activated T Cells by Nonleukemogenic Human T-Cell Leukemia Virus Type 2 but Not by Leukemogenic Type 1 Virus
    American Society for Microbiology ; 2005
    In:  Journal of Virology Vol. 79, No. 18 ( 2005-09-15), p. 11925-11934
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 79, No. 18 ( 2005-09-15), p. 11925-11934
    Abstract: Human T-cell leukemia virus type 1 (HTLV-1) but not HTLV-2 is associated with adult T-cell leukemia. We found that HTLV-2 Tax2 protein stimulated reporter gene expression regulated by the interleukin (IL)-2 promoter through the nuclear factor of activated T cells (NFAT) in a human T-cell line (Jurkat). However, the activity of HTLV-1 Tax1 was minimal in this system. T-cell lines immortalized by HTLV-2 but not HTLV-1 constitutively exhibited activated NFAT in the nucleus and constitutively expressed IL-2 mRNA. Cyclosporine A, an inhibitor of NFAT activation, abrogated the induction of IL-2 mRNA in HTLV-2-immortalized T-cell lines and concomitantly inhibited cell growth. This growth inhibition was rescued by the addition of IL-2 to the culture. Furthermore, anti-IL-2 receptor antibodies significantly reduced the proliferation of HTLV-2-infected T-cell lines but not that of HTLV-1-infected cells. Our results suggest that Tax2 activates an IL-2 autocrine loop mediated through NFAT that supports the growth of HTLV-2-infected cells under low-IL-2 conditions. This mechanism would be especially important in vivo, where this autocrine mechanism establishes a nonleukemogenic life-long HTLV-2 infection. The results also suggest that differences in long-term cytokine production between HTLV-1 and HTLV-2 infection are another factor for the differences in pathogenesis.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.79.18.11925-11934.2005
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2005
    detail.hit.zdb_id: 1495529-5
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  • 3
    Online Resource
    Online Resource
    Identification of TL-Om1, an Adult T-Cell Leukemia (ATL) Cell Line, as Reference Material for Quantitative PCR for Human T-Lymphotropic Virus 1
    American Society for Microbiology ; 2015
    In:  Journal of Clinical Microbiology Vol. 53, No. 2 ( 2015-02), p. 587-596
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 53, No. 2 ( 2015-02), p. 587-596
    Abstract: Quantitative PCR (qPCR) for human T-lymphotropic virus 1 (HTLV-1) is useful for measuring the amount of integrated HTLV-1 proviral DNA in peripheral blood mononuclear cells. Many laboratories in Japan have developed different HTLV-1 qPCR methods. However, when six independent laboratories analyzed the proviral load of the same samples, there was a 5-fold difference in their results. To standardize HTLV-1 qPCR, preparation of a well-defined reference material is needed. We analyzed the integrated HTLV-1 genome and the internal control (IC) genes of TL-Om1, a cell line derived from adult T-cell leukemia, to confirm its suitability as a reference material for HTLV-1 qPCR. Fluorescent in situ hybridization (FISH) showed that HTLV-1 provirus was monoclonally integrated in chromosome 1 at the site of 1p13 in the TL-Om1 genome. HTLV-1 proviral genome was not transferred from TL-Om1 to an uninfected T-cell line, suggesting that the HTLV-1 proviral copy number in TL-Om1 cells is stable. To determine the copy number of HTLV-1 provirus and IC genes in TL-Om1 cells, we used FISH, digital PCR, and qPCR. HTLV-1 copy numbers obtained by these three methods were similar, suggesting that their results were accurate. Also, the ratio of the copy number of HTLV-1 provirus to one of the IC genes, RNase P, was consistent for all three methods. These findings indicate that TL-Om1 cells are an appropriate reference material for HTLV-1 qPCR.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.02254-14
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2015
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Clathrin-Dependent Entry of Severe Acute Respiratory Syndrome Coronavirus into Target Cells Expressing ACE2 with the Cytoplasmic Tail Deleted
    American Society for Microbiology ; 2007
    In:  Journal of Virology Vol. 81, No. 16 ( 2007-08-15), p. 8722-8729
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 81, No. 16 ( 2007-08-15), p. 8722-8729
    Abstract: The penetration of various viruses into host cells is accomplished by hijacking the host endocytosis machinery. In the case of severe acute respiratory syndrome coronavirus (SARS-CoV) infection, viral entry is reported to require a low pH in intracytoplasmic vesicles; however, little is known about how SARS-CoV invades such compartments. Here we demonstrate that SARS-CoV mainly utilizes the clathrin-mediated endocytosis pathway for its entry to target cells by using infectious SARS-CoV, as well as a SARS-CoV pseudovirus packaged in the SARS-CoV envelope. The SARS-CoV entered caveolin-1-negative HepG2 cells, and the entry was significantly inhibited by treatment with chlorpromazine, an inhibitor for clathrin-dependent endocytosis, and by small interfering RNA-mediated gene silencing for the clathrin heavy chain. Furthermore, the SARS-CoV entered COS7 cells transfected with the mutant of ACE2 with the cytoplasmic tail deleted, SARS-CoV receptor, as well as the wild-type ACE2, and their entries were significantly inhibited by treatment with chlorpromazine. In addition, ACE2 translocated into EEA1-positive early endosomes immediately after the virus attachment to ACE2. These results suggest that when SARS-CoV binds ACE2 it is internalized and penetrates early endosomes in a clathrin-dependent manner and that the cytoplasmic tail of ACE2 is not required for the penetration of SARS-CoV.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.00253-07
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2007
    detail.hit.zdb_id: 1495529-5
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  • 5
    Online Resource
    Online Resource
    Human Parvovirus B19 Nonstructural Protein (NS1) Induces Cell Cycle Arrest at G 1 Phase
    American Society for Microbiology ; 2003
    In:  Journal of Virology Vol. 77, No. 5 ( 2003-03), p. 2915-2921
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 77, No. 5 ( 2003-03), p. 2915-2921
    Abstract: Human parvovirus B19 infects predominantly erythroid precursor cells, leading to inhibition of erythropoiesis. This erythroid cell damage is mediated by the viral nonstructural protein 1 (NS1) through an apoptotic mechanism. We previously demonstrated that B19 virus infection induces G 2 arrest in erythroid UT7/Epo-S1 cells; however, the role of NS1 in regulating cell cycle arrest is unknown. In this report, by using paclitaxel, a mitotic inhibitor, we show that B19 virus infection induces not only G 2 arrest but also G 1 arrest. Interestingly, UV-irradiated B19 virus, which has inactivated the expression of NS1, still harbors the ability to induce G 2 arrest but not G 1 arrest. Furthermore, treatment with caffeine, a G 2 checkpoint inhibitor, abrogated the B19 virus-induced G 2 arrest despite expression of NS1. These results suggest that the B19 virus-induced G 2 arrest is not mediated by NS1 expression. We also found that NS1-transfected UT7/Epo-S1 and 293T cells induced cell cycle arrest at the G 1 phase. These results indicate that NS1 expression plays a critical role in G 1 arrest induced by B19 virus. Furthermore, NS1 expression significantly increased p21/WAF1 expression, a cyclin-dependent kinase inhibitor that induces G 1 arrest. Thus, G 1 arrest mediated by NS1 may be a prerequisite for the apoptotic damage of erythroid progenitor cells upon B19 virus infection.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.77.5.2915-2921.2003
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2003
    detail.hit.zdb_id: 1495529-5
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  • 6
    Online Resource
    Online Resource
    Human Parvovirus B19 Nonstructural (NS1) Protein Induces Apoptosis in Erythroid Lineage Cells
    American Society for Microbiology ; 1998
    In:  Journal of Virology Vol. 72, No. 4 ( 1998-04), p. 3018-3028
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 72, No. 4 ( 1998-04), p. 3018-3028
    Abstract: Infection of erythroid-lineage cells by human parvovirus B19 is characterized by a gradual cytocidal effect. Accumulating evidence now implicates the nonstructural (NS1) protein of the virus in cytotoxicity, but the mechanism underlying the NS1-induced cell death is not known. Using a stringent regulatory system, we demonstrate that NS1 cytotoxicity is closely related to apoptosis, as evidenced by cell morphology, genomic DNA fragmentation, and cell cycle analysis with the human erythroleukemia cell line K562 and the erythropoietin-dependent megakaryocytic cell line UT-7/Epo. Apoptosis was significantly inhibited by an interleukin-1β (IL-1β)-converting enzyme (ICE)/CED-3 family protease inhibitor, Ac-DEVD-CHO (CPP32; caspase 3), whereas a similar inhibitor of ICE (caspase 1), Ac-YVAD-CHO, had no effect. Furthermore, stable expression of the human Bcl-2 proto-oncogene resulted in near-total protection from cell death in response to NS1 induction. Mutations engineered into the nucleoside triphosphate-binding domain of NS1 significantly rescued cells from NS1-induced apoptosis without having any effect on NS1-induced activation of the IL-6 gene expression which is mediated by NF-κB. Furthermore, using pentoxifylline, an inhibitor of NF-κB activation, we demonstrate that the NF-κB-mediated IL-6 activation by NS1 is uncoupled from the apoptotic pathway. This functional dissection indicates a complexity underlying the biochemical function of human parvovirus NS1 in transcriptional activation and induction of apoptosis. Our findings indicate that NS1 of parvovirus B19 induces cell death by apoptosis in at least erythroid-lineage cells by a pathway that involves caspase 3, whose activation may be a key event during NS1-induced cell death.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/JVI.72.4.3018-3028.1998
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1998
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