EBNA3C interacts with Gadd34 and counteracts the unfolded protein response

EBNA3C is an EBV-encoded nuclear protein, essential for proliferation of EBV infected B-lymphocytes. Using EBNA3C amino acids 365-545 in a yeast two hybrid screen, we found an interaction with the Growth Arrest and DNA-damage protein, Gadd34. When both proteins are overexpressed, Gadd34 can interact with EBNA3C in both nuclear and cytoplasmic compartments. Amino acids 483-610 of Gadd34, including the two PP1a interaction, and the HSV-1 ICPγ34.5 homology domains, are required for the interaction. Furthermore, interaction is lost with a mutant of EBNA3C (509 DVIEVID 515→AVIAVIA), that abolishes EBNA3C coactivation ability as well as SUMO interaction[1]. In B-cells, Gadd34, and EBNA3C are present in a complex with PP1a using microcystin sepharose affinity purification, Using a lymphoblastoid cell line in which EBNA3C protein levels are conditional on hydroxytamoxifen, surprisingly, we found that (i) EBNA3C maintains phosphorylation of eIF2α at serine 51, and (ii) protects against ER stress induced activation of the unfolded protein response as measured by XBP1 (u) versus XBP1(s) protein expression and N-terminal ATF6 cleavage. In reporter assays, overexpression of Gadd34 enhances EBNA3C's ability to co-activate EBNA2 activation of the LMP1 promoter. Collectively the data suggest that EBNA3C interacts with Gadd34, activating the upstream component of the UPR (eIF2α phosphorylation) while preventing downstream UPR events (XBP1 activation and ATF6 cleavage)

Characterization of epstein-barr virus-infected mantle cell lymphoma lines.

It has been reported that Epstein-Barr virus (EBV) resides in resting B cells in vivo. However, an ideal in vitro system for studying EBV latent infection in vivo has not yet been established. In this study, a mantle cell lymphoma line, SP53, was successfully infected with a recombinant EBV containing a neomycin-resistant gene. The EBV-carrying SP53 cells were obtained by selection using G418. They expressed EBER-1, EBNAs, and LMP1; this expression pattern of the EBV genes was similar to that in a lymphoblastoid cell line (LCL). However, proliferation assay showed that the EBV-carrying SP53 cells have a doubling time of 73 h, compared with 57 h of SP53 cells. Transplantation of 10(8) SP53 cells to nude mice formed tumors in 4 of 10 mice inoculated, but the EBV-carrying SP53 cells did not. Unexpectedly, EBV infection reduced the proliferation and tumorigenicity of SP53 cells. However, the EBV-carrying SP53 cells showed higher resistance to apoptosis induced by serum starvation than did the SP53 cells. The inhibition of proliferation and the resistance to apoptosis induced in SP53 cells by EBV infection indicate that this cell line might to some extent provide a model of in vivo EBV reservoir cells.</p

Unexpected Instability of Family of Repeats (FR), the Critical cis-Acting Sequence Required for EBV Latent Infection, in EBV-BAC Systems

A group of repetitive sequences, known as the Family of Repeats (FR), is a critical cis-acting sequence required for EBV latent infection. The FR sequences are heterogeneous among EBV strains, and they are sometimes subject to partial deletion when subcloned in E. coli-based cloning vectors. However, the FR stability in EBV-BAC (bacterial artificial chromosome) system has never been investigated. We found that the full length FR of the Akata strain EBV was not stably maintained in a BAC vector. By contrast, newly obtained BAC clones of the B95-8 strain of EBV stably maintained the full length FR during recombinant virus production and B-cell transformation. Investigation of primary DNA sequences of Akata–derived EBV-BAC clones indicates that the FR instability is most likely due to a putative secondary structure of the FR region. We conclude that the FR instability in EBV-BAC clones can be a pitfall in E. coli-mediated EBV genetics

Treatment of Marmoset Intracerebral Hemorrhage with Humanized Anti-HMGB1 mAb

Intracerebral hemorrhage (ICH) is recognized as a severe clinical problem lacking effective treatment. High mobility group box-1 (HMGB1) exhibits inflammatory cytokine-like activity once released into the extracellular space from the nuclei. We previously demonstrated that intravenous injection of rat anti-HMGB1 monoclonal antibody (mAb) remarkably ameliorated brain injury in a rat ICH model. Therefore, we developed a humanized anti-HMGB1 mAb (OKY001) for clinical use. The present study examined whether and how the humanized anti-HMGB1 mAb ameliorates ICH injury in common marmosets. The results show that administration of humanized anti-HMGB1 mAb inhibited HMGB1 release from the brain into plasma, in association with a decrease of 4-hydroxynonenal (4-HNE) accumulation and a decrease in cerebral iron deposition. In addition, humanized anti-HMGB1 mAb treatment resulted in a reduction in brain injury volume at 12 d after ICH induction. Our in vitro experiment showed that recombinant HMGB1 inhibited hemoglobin uptake by macrophages through CD163 in the presence of haptoglobin, suggesting that the release of excess HMGB1 from the brain may induce a delay in hemoglobin scavenging, thereby allowing the toxic effects of hemoglobin, heme, and Fe2+ to persist. Finally, humanized anti-HMGB1 mAb reduced body weight loss and improved behavioral performance after ICH. Taken together, these results suggest that intravenous injection of humanized anti-HMGB1 mAb has potential as a novel therapeutic strategy for ICH

The Type Ic Hypernova SN 2002ap

Photometric and spectroscopic data of the energetic Type Ic supernova (SN) 2002ap are presented, and the properties of the SN are investigated through models of its spectral evolution and its light curve. The SN is spectroscopically similar to the "hypernova" SN 1997ef. However, its kinetic energy [$\sim (4-10) \times 10^{51}$ erg] and the mass ejected (2.5-5 $M_{\odot}$) are smaller, resulting in a faster-evolving light curve. The SN synthesized $\sim 0.07 M_{\odot}$ of $^{56}$Ni, and its peak luminosity was similar to that of normal SNe. Brightness alone should not be used to define a hypernova, whose defining character, namely very broad spectral features, is the result of a high kinetic energy. The likely main-sequence mass of the progenitor star was 20-25 $M_{\odot}$, which is also lower than that of both hypernovae SNe 1997ef and 1998bw. SN 2002ap appears to lie at the low-energy and low-mass end of the hypernova sequence as it is known so far. Observations of the nebular spectrum, which is expected to dominate by summer 2002, are necessary to confirm these values.Comment: 10 pages, 4 figures, accepted for publication in ApJL, 30 April 2002 (minor changes to match the accepted version, with figures being colored

Breast cancer cell lines carry cell line-specific genomic alterations that are distinct from aberrations in breast cancer tissues: Comparison of the CGH profiles between cancer cell lines and primary cancer tissues

<p>Abstract</p> <p>Background</p> <p>Cell lines are commonly used in various kinds of biomedical research in the world. However, it remains uncertain whether genomic alterations existing in primary tumor tissues are represented in cell lines and whether cell lines carry cell line-specific genomic alterations. This study was performed to answer these questions.</p> <p>Methods</p> <p>Array-based comparative genomic hybridization (CGH) was employed with 4030 bacterial artificial chromosomes (BACs) that cover the genome at 1.0 megabase resolution to analyze DNA copy number aberrations (DCNAs) in 35 primary breast tumors and 24 breast cancer cell lines. DCNAs were compared between these two groups. A tissue microdissection technique was applied to primary tumor tissues to reduce the contamination of samples by normal tissue components.</p> <p>Results</p> <p>The average number of BAC clones with DCNAs was 1832 (45.3% of spotted clones) and 971 (24.9%) for cell lines and primary tumor tissues, respectively. Gains of 1q and 8q and losses of 8p, 11q, 16q and 17p were detected in >50% of primary cancer tissues. These aberrations were also frequently detected in cell lines. In addition to these alterations, the cell lines showed recurrent genomic alterations including gains of 5p14-15, 20q11 and 20q13 and losses of 4p13-p16, 18q12, 18q21, Xq21.1 and Xq26-q28 that were barely detected in tumor tissue specimens. These are considered to be cell line-specific DCNAs. The frequency of the HER2 amplification was high in both cell lines and tumor tissues, but it was statistically different between cell lines and primary tumors (P = 0.012); 41.3 ± 29.9% for the cell lines and 15.9 ± 18.6% for the tissue specimens.</p> <p>Conclusions</p> <p>Established cell lines carry cell lines-specific DCNAs together with recurrent aberrations detected in primary tumor tissues. It must therefore be emphasized that cell lines do not always represent the genotypes of parental tumor tissues.</p

Epstein-Barr Virus BGLF4 Kinase Retards Cellular S-Phase Progression and Induces Chromosomal Abnormality

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

Replication of Epstein-Barr Virus Primary Infection in Human Tonsil Tissue Explants

Epstein-Barr virus (EBV) may cause a variety of virus-associated diseases, but no antiviral agents have yet been developed against this virus. Animal models are thus indispensable for the pathological analysis of EBV-related infections and the elucidation of therapeutic methods. To establish a model system for the study of EBV infection, we tested the ability of B95–8 virus and recombinant EBV expressing enhanced green fluorescent protein (EGFP) to replicate in human lymphoid tissue. Human tonsil tissues that had been surgically removed during routine tonsillectomy were sectioned into small blocks and placed on top of collagen sponge gels in culture medium at the air-interface, then a cell-free viral suspension was directly applied to the top of each tissue block. Increasing levels of EBV DNA in culture medium were observed after 12–15 days through 24 days post-infection in tissue models infected with B95–8 and EGFP-EBV. Expression levels of eight EBV-associated genes in cells collected from culture medium were increased during culture. EBV-encoded small RNA-positive cells were detected in the interfollicular areas in paraffin-embedded sections. Flow cytometric analyses revealed that most EGFP+ cells were CD3− CD56− CD19+ HLA-DR+, and represented both naïve (immunoglobulin D+) and memory (CD27+) B cells. Moreover, EBV replication in this model was suppressed by acyclovir treatment in a dose-dependent manner. These data suggest that this model has potential for use in the pathological analysis of local tissues at the time of primary infection, as well as for screening novel antiviral agents