bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient Replication of Epstein-Barr Virus-Derived Plasmids Requires Tethering by EBNA1 to Host Chromosomes
Authors: Hodin Theresa L. , Najrana Tanbir , Yates John L. 
Published: September 2013

ABSTRACT

The EBNA1 protein of Epstein-Barr virus enables plasmids carrying
oriP
both to duplicate and to segregate efficiently in proliferating cells. EBNA1 recruits the origin recognition complex (ORC) to establish a replication origin at one element of
oriP
, DS (
d
yad
s
ymmetry); at another element, FR (
f
amily of
r
epeats), EBNA1 binds to an array of sites from which it tethers plasmids to host chromosomes for mitotic stability. We report experiments leading to the conclusion that tethering by EBNA1 to host chromosomes is also needed within interphase nuclei in order for plasmids to be replicated efficiently from
oriP
. The DNA-binding domain of EBNA1, which lacks chromosome-binding ability, was found to support weak, DS-specific replication in HEK293 cells after transient transfection, being 17% as active as wild-type EBNA1. The low efficiency of replication was not due to the failure of the DNA-binding domain to retain plasmids within nuclei, because plasmids were recovered in similar amounts and entirely from the nuclear fraction of these transiently transfected cells. A derivative of EBNA1 with its chromosome-tethering domains replaced by a 22-amino-acid nucleosome-binding domain was fully active in supporting
oriP
functions. The implication is that EBNA1's DNA-binding domain is able to recruit ORC to DS, but either this step or subsequent replication is only efficient if the plasmid is tethered to a host chromosome. Finally, with some cell lines, DS can hardly support even transient plasmid replication without FR. A loss of plasmids lacking FR from nuclei cannot account for this requirement, suggesting that the stronger tethering to chromosomes by FR is needed for plasmid replication within the nuclei of such cells.
The T Antigen Locus of Merkel Cell Polyomavirus Downregulates Human Toll-Like Receptor 9 Expression
Authors: Shahzad Naveed , Shuda Masahiro , Gheit Tarik , Kwun Hyun Jin , Cornet Iris , Saidj Djamel , Zannetti Claudia , Hasan Uzma , Chang Yuan , Moore Patrick S. , Accardi Rosita , Tommasino Massimo 
Published: September 2013

ABSTRACT
Establishment of a chronic infection is a key event in virus-mediated carcinogenesis. Several cancer-associated, double-stranded DNA (dsDNA) viruses act via their oncoproteins to downregulate Toll-like receptor 9 (TLR9), a key receptor in the host innate immune response that senses viral or bacterial dsDNA. A novel oncogenic virus, Merkel cell polyomavirus (MCPyV), has been recently identified that causes up to 80% of Merkel cell carcinomas (MCCs). However, it is not yet known whether this oncogenic virus also disrupts immune-related pathways. We find that MCPyV large T antigen (LT) expression downregulates TLR9 expression in epithelial and MCC-derived cells. Accordingly, silencing of LT expression results in upregulation of mRNA TLR9 levels. In addition, small T antigen (sT) also appears to inhibit TLR9 expression, since inhibition of its expression also resulted in an increase of TLR9 mRNA levels. LT inhibits TLR9 expression by decreasing the mRNA levels of the C/EBPβ transactivator, a positive regulator of the TLR9 promoter. Chromatin immunoprecipitation reveals that C/EBPβ binding at a C/EBPβ response element (RE) in the TLR9 promoter is strongly inhibited by expression of MCPyV early genes and that mutation of the C/EBP RE prevents MCPyV downregulation of TLR9. A survey of BK polyomavirus (BKPyV), JC polyomavirus (JCPyV), KI polyomavirus (KIPyV), MCPyV, simian virus 40 (SV40), and WU polyomavirus (WUPyV) early genes revealed that only BKPyV and MCPyV are potent inhibitors of TLR9 gene expression. MCPyV LT targeting of C/EBP transactivators is likely to play an important role in viral persistence and potentially inhibit host cell immune responses during MCPyV tumorigenesis.
The L Gene of J Paramyxovirus Plays a Critical Role in Viral Pathogenesis
Authors: Li Zhuo , Xu Jie , Chen Zhenhai , Gao Xiudan , Wang Lin-Fa , Basler Christopher , Sakamoto Kaori , He Biao 
Published: September 2013

ABSTRACT
J paramyxovirus (JPV) was first isolated from moribund mice with hemorrhagic lung lesions in Australia in the 1970s. Recent sequencing of JPV (JPV-LW) confirms that JPV is a paramyxovirus with several unique features. However, neither JPV-LW nor a recombinant JPV based on its sequence (rJPV-LW) caused obvious illness in mice. In this work, we analyzed a different JPV isolate (JPV-BH), which behaved differently from JPV-LW; JPV-BH grew more slowly in Vero cells and had less of a cytopathic effect on tissue culture cells but caused severe disease in mice. We have determined the whole genome sequence of JPV-BH. There were several nucleotide sequence differences between JPV-BH and JPV-LW, one in the leader sequence, one in the GX gene, and three in the L gene. The high sequence identity between JPV-BH and JPV-LW suggests that JPV-BH and JPV-LW are the same virus strain but were obtained at different passages from different laboratories. To understand the roles of these nucleotide sequence differences in pathogenicity in mice, we generated a recombinant JPV-BH strain (rJPV-BH) and hybrid rJPV-BH strains with sequences from the leader sequence (rJPV-BH-Le-LW), the GX gene (rJPV-BH-GX-LW), and the L gene (rJPV-BH-L-LW) of JPV-LW and compared their pathogenicities in mice. We have found that rJPV-BH-L-LW was attenuated in mice, indicating that nucleotide sequence differences in the L gene play a critical role in pathogenesis.
Novel Apoptosis Suppressor Apsup from the Baculovirus Lymantria dispar Multiple Nucleopolyhedrovirus Precludes Apoptosis by Preventing Proteolytic Processing of Initiator Caspase Dronc
Authors: Yamada Hayato , Kitaguchi Koji , Hamajima Rina , Kobayashi Michihiro , Ikeda Motoko 
Published: September 2013

ABSTRACT

We previously identified a novel baculovirus-encoded apoptosis suppressor, Apsup, from the baculovirus
Lymantria dispar
multiple nucleopolyhedrovirus (LdMNPV). Apsup inhibits the apoptosis of
L. dispar
Ld652Y cells triggered by infection with
p35
-defective
Autographa californica
MNPV (vAcΔp35) and exposure to actinomycin D or UV light. Here, we examined the functional role of Apsup in apoptosis regulation in insect cells. Apsup prevented apoptosis and the proteolytic processing of
L. dispar
initiator caspase Dronc (Ld-Dronc) in Ld652Y cells triggered by overexpression of Ld-Dronc, LdMNPV inhibitor-of-apoptosis 3 (IAP3), or
Hyphantria cunea
MNPV IAP1. In vAcΔp35-infected apoptotic Ld652Y cells, Apsup restricted apoptosis induction and prevented processing of endogenous Ld-Dronc. Conversely, upon RNA interference (RNAi)-mediated silencing of
apsup
, LdMNPV-infected Ld652Y cells, which typically support high-titer virus replication, underwent apoptosis, accompanied by the processing of endogenous Ld-Dronc. Furthermore, endogenous Ld-Dronc coimmunoprecipitated with transiently expressed Apsup, indicating that Apsup physically interacts with Ld-Dronc. Apsup prevented the apoptosis of Sf9 cells triggered by vAcΔp35 infection but did not inhibit apoptosis or activation of caspase-3-like protease in vAcΔp35-infected
Drosophila melanogaster
S2 cells. Apsup also inhibited the proteolytic processing of
L. dispar
effector caspase Ld-caspase-1 in the transient expression assay but did not physically interact with Ld-caspase-1. These results demonstrate that Apsup inhibits apoptosis in Ld652Y cells by preventing the proteolytic processing of Ld-Dronc. Together with our previous findings showing that Apsup prevents the processing of both overexpressed Ld-Dronc and
Bombyx mori
Dronc, these results also demonstrate that Apsup functions as an effective apoptotic suppressor in various lepidopteran, but not dipteran, insect cells.
Configuration of Viral Ribonucleoprotein Complexes within the Influenza A Virion
Authors: Sugita Yukihiko , Sagara Hiroshi , Noda Takeshi , Kawaoka Yoshihiro 
Published: September 2013

ABSTRACT
The influenza A virus possesses an eight-segmented, negative-sense, single-stranded RNA genome (vRNA). Each vRNA segment binds to multiple copies of viral nucleoproteins and a small number of heterotrimeric polymerase complexes to form a rod-like ribonucleoprotein complex (RNP), which is essential for the transcription and replication of the vRNAs. However, how the RNPs are organized within the progeny virion is not fully understood. Here, by focusing on polymerase complexes, we analyzed the fine structure of purified RNPs and their configuration within virions by using various electron microscopies (EM). We confirmed that the individual RNPs possess a single polymerase complex at one end of the rod-like structure and that, as determined using immune EM, some RNPs are incorporated into budding virions with their polymerase-binding ends at the budding tip, whereas others align with their polymerase-binding ends at the bottom of the virion. These data further our understanding of influenza virus virion morphogenesis.
Characterization of Mus musculus Papillomavirus 1 Infection
In Situ
Reveals an Unusual Pattern of Late Gene Expression and Capsid Protein Localization
Authors: Handisurya Alessandra , Day Patricia M. , Thompson Cynthia D. , Buck Christopher B. , Pang Yuk-Ying S. , Lowy Douglas R. , Schiller John T. 
Published: September 2013

ABSTRACT

Full-length genomic DNA of the recently identified laboratory mouse papillomavirus 1 (MusPV1) was synthesized
in vitro
and was used to establish and characterize a mouse model of papillomavirus pathobiology. MusPV1 DNA, whether naked or encapsidated by MusPV1 or human papillomavirus 16 (HPV 16) capsids, efficiently induced the outgrowth of papillomas as early as 3 weeks after application to abraded skin on the muzzles and tails of athymic NCr nude mice. High concentrations of virions were extracted from homogenized papillomatous tissues and were serially passaged for >10 generations. Neutralization by L1 antisera confirmed that infectious transmission was capsid mediated. Unexpectedly, the skin of the murine back was much less susceptible to virion-induced papillomas than the muzzle or tail. Although reporter pseudovirions readily transduced the skin of the back, infection with native MusPV1 resulted in less viral genome amplification and gene expression on the back, including reduced expression of the L1 protein and very low expression of the L2 protein, results that imply skin region-specific control of postentry aspects of the viral life cycle. Unexpectedly, L1 protein on the back was predominantly cytoplasmic, while on the tail the abundant L1 was cytoplasmic in the lower epithelial layers and nuclear in the upper layers. Nuclear localization of L1 occurred only in cells that coexpressed the minor capsid protein, L2. The pattern of L1 protein staining in the infected epithelium suggests that L1 expression occurs earlier in the MusPV1 life cycle than in the life cycle of high-risk HPV and that virion assembly is regulated by a previously undescribed mechanism.
Herpes Simplex Virus 1 Counteracts Tetherin Restriction via Its Virion Host Shutoff Activity
Authors: Zenner Helen L. , Mauricio Rui , Banting George , Crump Colin M. 
Published: September 2013

ABSTRACTThe interferon-inducible membrane protein tetherin (Bst-2, or CD317) is an antiviral factor that inhibits enveloped virus release by cross-linking newly formed virus particles to the producing cell. The majority of viruses that are sensitive to tetherin restriction appear to be those that acquire their envelopes at the plasma membrane, although many viruses, including herpesviruses, envelope at intracellular membranes, and the effect of tetherin on such viruses has been less well studied. We investigated the tetherin sensitivity and possible countermeasures of herpes simplex virus 1 (HSV-1). We found that overexpression of tetherin inhibits HSV-1 release and that HSV-1 efficiently depletes tetherin from infected cells. We further show that the virion host shutoff protein (Vhs) is important for depletion of tetherin mRNA and protein and that removal of tetherin compensates for defects in replication and release of a Vhs-null virus. Vhs is known to be important for HSV-1 to evade the innate immune responsein vivo. Taken together, our data suggest that tetherin has antiviral activity toward HSV-1 and that the removal of tetherin by Vhs is important for the efficient replication and dissemination of HSV-1.
Replication Stress and Mitotic Dysfunction in Cells Expressing Simian Virus 40 Large T Antigen
Authors: Hu Liang , Filippakis Harilaos , Huang Haomin , Yen Timothy J. , Gjoerup Ole V. 
Published: September 2013

ABSTRACT
We previously demonstrated that simian virus 40 (SV40) large T antigen (LT) binds to the Bub1 kinase, a key regulator of the spindle checkpoint and chromosome segregation. Bub1 mutations or altered expression patterns are linked to chromosome missegregation and are considered to be a driving force in some human cancers. Here we report that LT, dependent on Bub1 binding, causes micronuclei, lagging chromatin, and anaphase bridges, which are hallmarks of chromosomal instability (CIN) and Bub1 insufficiency. Using time-lapse microscopy, we demonstrate that LT imposes a Bub1 binding-dependent delay in the metaphase-to-anaphase transition. Kinetochore fibers reveal that LT, via Bub1 binding, causes aberrant kinetochore (KT)-microtubule (MT) attachments and a shortened interkinetochore distance, consistent with a lack of tension. Previously, we showed that LT also induces the DNA damage response (DDR) via Bub1 binding. Using inducible LT cell lines, we show that an activated DDR was observed before the appearance of anaphase bridges and micronuclei. Furthermore, LT induction in serum-starved cells demonstrated γ-H2AX accumulation in cells that had not yet entered mitosis. Thus, DDR activation can occur independently of chromosome segregation defects. Replication stress pathways may be responsible, because signatures of replication stress were observed, which were attenuated by exogenous supplementation with nucleosides. Our observations allow us to propose a model that explains and integrates the diverse manifestations of genomic instability induced by LT.
Polycomb Repressive Complex 2 Silences Human Cytomegalovirus Transcription in Quiescent Infection Models
Authors: Abraham Christopher G. , Kulesza Caroline A. 
Published: September 2013

ABSTRACT
Chromatin-based regulation of herpesviral transcriptional programs is increasingly appreciated as a mechanism for modulating infection outcomes. Transcriptionally permissive euchromatin predominates during lytic infection, whereas heterochromatin domains refractory to transcription are enriched at lytic genes during latency. Reversibly silenced facultative heterochromatin domains are often enriched for histone H3 trimethylated on lysine 27 (H3K27me3), a modification catalyzed by Polycomb repressive complex 2 (PRC2). The requirement for PRC2 in suppressing the human cytomegalovirus (HCMV) lytic transcriptional program during latency has not been thoroughly evaluated. Therefore, we disrupted PRC2 activity in the highly tractable THP1 and NT2D1 quiescent-infection models by treating cells with small-molecule inhibitors of PRC2 activity. Compared to control cells, disruption of PRC2 in HCMV-infected THP1 or NT2D1 cells resulted in significant increases in viral transcript levels and the detection of viral protein. Using chromatin immunoprecipitation, we demonstrated that enrichment of H3K27me3, deposited by PRC2, correlates inversely with lytic transcriptional output, suggesting that PRC2 catalytic activity at viral chromatin directly represses lytic transcription. Together, our data suggest that PRC2-mediated repression of viral transcription is a key step in the establishment and maintenance of HCMV latency.
Structure of the Fusion Core and Inhibition of Fusion by a Heptad Repeat Peptide Derived from the S Protein of Middle East Respiratory Syndrome Coronavirus
Authors: Gao Jing , Lu Guangwen , Qi Jianxun , Li Yan , Wu Ying , Deng Yao , Geng Heyuan , Li Hongbin , Wang Qihui , Xiao Haixia , Tan Wenjie , Yan Jinghua , Gao George F. 
Published: September 2013

ABSTRACT
Middle East respiratory syndrome coronavirus (MERS-CoV) recently emerged as a severe worldwide public health concern. The virus is highly pathogenic, manifesting in infected patients with an approximately 50% fatality rate. It is known that the surface spike (S) proteins of coronaviruses mediate receptor recognition and membrane fusion, thereby playing an indispensable role in initiating infection. In this process, heptad repeats 1 and 2 (HR1 and HR2) of the S protein assemble into a complex called the fusion core, which represents a key membrane fusion architecture. To date, however, the MERS-CoV fusion core remains uncharacterized. In this study, we performed a series of biochemical and biophysical analyses characterizing the HR1/HR2 complexes of this novel virus. The HR sequences were variably truncated and then connected with a flexible amino acid linker. In each case, the recombinant protein automatically assembled into a trimer in solution, displaying a typical α-helical structure. One of these trimers was successfully crystallized, and its structure was solved at a resolution of 1.9 Å. A canonical 6-helix bundle, like those reported for other coronaviruses, was revealed, with three HR1 helices forming the central coiled-coil core and three HR2 chains surrounding the core in the HR1 side grooves. This demonstrates that MERS-CoV utilizes a mechanism similar to those of other class I enveloped viruses for membrane fusion. With this notion, we further identified an HR2-based peptide that could potently inhibit MERS-CoV fusion and entry by using a pseudotyped-virus system. These results lay the groundwork for future inhibitory peptidic drug design.
Parvovirus B19 Uptake Is a Highly Selective Process Controlled by VP1u, a Novel Determinant of Viral Tropism
Authors: Leisi Remo , Ruprecht Nico , Kempf Christoph , Ros Carlos 
Published: September 2013

ABSTRACT
The VP1 unique region (VP1u) of human parvovirus B19 (B19V) is the immunodominant part of the viral capsid. Originally inaccessible, the VP1u becomes exposed upon primary attachment to the globoside receptor. To study the function of the exposed VP1u in B19V uptake, we expressed this region as a recombinant protein. Here, we report that purified recombinant VP1u binds and is internalized in UT7/Epo cells. By means of truncations and specific antibodies, we identified the most N-terminal amino acid residues of VP1u as the essential region for binding and internalization. Furthermore, the recombinant VP1u was able to block B19V uptake, suggesting that the protein and the virus undertake the same internalization pathway. Assays with different erythroid and nonerythroid cell lines showed that the N-terminal VP1u binding was restricted to a few cell lines of the erythroid lineage, which were also the only cells that allowed B19V internalization and infection. These results together indicate that the N-terminal region of VP1u is responsible for the internalization of the virus and that the interacting receptor is restricted to B19V-susceptible cells. The highly selective uptake mechanism represents a novel determinant of the tropism and pathogenesis of B19V.
Phylogenomic Network and Comparative Genomics Reveal a Diverged Member of the ϕKZ-Related Group, Marine Vibrio Phage ϕJM-2012
Authors: Jang Ho Bin , Fagutao Fernand F. , Nho Seong Won , Park Seong Bin , Cha In Seok , Yu Jong Earn , Lee Jung Seok , Im Se Pyeong , Aoki Takashi , Jung Tae Sung 
Published: September 2013

ABSTRACT

Bacteriophages are the largest reservoir of genetic diversity. Here we describe the novel phage ϕJM-2012. This natural isolate from marine
Vibrio cyclitrophicus
possesses very few gene contents relevant to other well-studied marine
Vibrio
phages. To better understand its evolutionary history, we built a mathematical model of pairwise relationships among 1,221 phage genomes, in which the genomes (nodes) are linked by edges representing the normalized number of shared orthologous protein families. This weighted network revealed that ϕJM-2012 was connected to only five members of the
Pseudomonas
ϕKZ-like phage family in an isolated network, strongly indicating that it belongs to this phage group. However, comparative genomic analyses highlighted an almost complete loss of colinearity with the ϕKZ-related genomes and little conservation of gene order, probably reflecting the action of distinct evolutionary forces on the genome of ϕJM-2012. In this phage, typical conserved core genes, including six RNA polymerase genes, were frequently displaced and the hyperplastic regions were rich in both unique genes and predicted unidirectional promoters with highly correlated orientations. Further, analysis of the ϕJM-2012 genome showed that segments of the conserved N-terminal parts of ϕKZ tail fiber paralogs exhibited evidence of combinatorial assortment, having switched transcriptional orientation, and there was recruitment and/or structural changes among phage endolysins and tail spike protein. Thus, this naturally occurring phage appears to have branched from a common ancestor of the ϕKZ-related groups, showing a distinct genomic architecture and unique genes that most likely reflect adaptation to its chosen host and environment.
Oral health and impact on performance of athletes participating in the London 2012 Olympic Games: a cross-sectional study
Authors: Needleman I , Ashley P , Petrie A , Fortune F , Turner W , Jones J , Niggli J , Engebretsen L , Budgett R , Donos N , Clough T , Porter S 
Published: September 2013

BackgroundOral health is important both for well-being and successful elite sporting performance. Reports from Olympic Games have found significant treatment needs; however, few studies have examined oral health directly. The aim of this study was to evaluate oral health, the determinants of oral health and the effect of oral health on well-being, training and performance of athletes participating in the London 2012 Games.MethodsCross-sectional study at the dental clinic within the Polyclinic in the athletes’ village. Following informed consent, a standardised history, clinical examination and brief questionnaire were conducted.Results302 athletes from 25 sports were recruited with data available for 278. The majority of athletes were from Africa, the Americas and Europe. Overall, the results demonstrated high levels of poor oral health including dental caries (55% athletes), dental erosion (45% athletes) and periodontal disease (gingivitis 76% athletes, periodontitis 15% athletes). More than 40% of athletes were ‘bothered’ by their oral health with 28% reporting an impact on quality of life and 18% on training and performance. Nearly half of the participants had not undergone a dental examination or hygiene care in the previous year.ConclusionsThe oral health of athletes attending the dental clinic of the London 2012 Games was poor with a resulting substantial negative impact on well-being, training and performance. As oral health is an important element of overall health and well-being, health promotion and disease prevention interventions are urgently required to optimise athletic performance.