bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of thePseudomonas putidaMobile Genetic Element ISPpu10: an Occupant of Repetitive Extragenic Palindromic Sequences
Authors: Ramos-González María Isabel , Campos María Jesús , Ramos Juan Luis , Espinosa-Urgel Manuel 
Published: December 2005

ABSTRACTWe have characterized thePseudomonas putidaKT2440 insertion element ISPpu10. This insertion sequence encodes a transposase which exhibits homology to the transposases and specific recombinases of the Piv/Moov family, and no inverted repeats are present at the borders of its left and right ends, thus constituting a new member of the atypical IS110/IS492family. ISPpu10was found in at least seven identical loci in the KT2440 genome, and variants were identified having an extra insertion at distinct loci. ISPpu10always appeared within the core of specific repetitive extragenic palindromic (REP) sequences TCGCGGGTAAACCCGCTCCTAC, exhibiting high target stringency. One intragenic target was found associated with the truncation of a GGDEF/EAL domain protein. After active in vitro transposition to a plasmid-borne target, a duplication of the CT (underlined above) at the junction as a consequence of the ISPpu10insertion was experimentally demonstrated for the first time in the IS110/IS492family. The same duplication was observed after transposition of ISPpu10from a plasmid to the chromosome ofP. putidaDOT-T1E, an ISPpu10-free strain with REPs similar to those of strain KT2440. Plasmid ISPpu10-mediated rearrangements were observed in vivo under laboratory conditions and in the plant rhizosphere.
Identification of the Lower Baseplate Protein as the Antireceptor of the Temperate Lactococcal Bacteriophages TP901-1 and Tuc2009
Authors: Vegge Christina S. , Vogensen Finn K. , Mc Grath Stephen , Neve Horst , van Sinderen Douwe , Brøndsted Lone 
Published: December 2005

ABSTRACT

The first step in the infection process of tailed phages is recognition and binding to the host receptor. This interaction is mediated by the phage antireceptor located in the distal tail structure. The temperate
Lactococcus lactis
phage TP901-1 belongs to the P335 species of the
Siphoviridae
family, which also includes the related phage Tuc2009. The distal tail structure of TP901-1 is well characterized and contains a double-disk baseplate and a central tail fiber. The structural tail proteins of TP901-1 and Tuc2009 are highly similar, but the phages have different host ranges and must therefore encode different antireceptors. In order to identify the antireceptors of TP901-1 and Tuc2009, a chimeric phage was generated in which the gene encoding the TP901-1 lower baseplate protein (

bppL
TP901-1

) was exchanged with the analogous gene (

orf53
2009

) of phage Tuc2009. The chimeric phage (TP901-1C) infected the Tuc2009 host strain efficiently and thus displayed an altered host range compared to TP901-1. Genomic analysis and sequencing verified that TP901-1C is a TP901-1 derivative containing the

orf53
2009

gene in exchange for

bppL
TP901-1

; however, a new sequence in the late promoter region was also discovered. Protein analysis confirmed that TP901-1C contains ORF53
2009
and not the lower baseplate protein BppL
TP901-1
, and it was concluded that BppL
TP901-1
and ORF53
2009
constitute antireceptor proteins of TP901-1 and Tuc2009, respectively. Electron micrographs revealed altered baseplate morphology of TP901-1C compared to that of the parental phage.
Identification and Characterization of the Genes Involved in Glycosylation Pathways of Mycobacterial Glycopeptidolipid Biosynthesis
Authors: Miyamoto Yuji , Mukai Tetsu , Nakata Noboru , Maeda Yumi , Kai Masanori , Naka Takashi , Yano Ikuya , Makino Masahiko 
Published: December 2005

ABSTRACTGlycopeptidolipids (GPLs) are major components present on the outer layers of the cell walls of several nontuberculous mycobacteria. GPLs are antigenic molecules and have variant oligosaccharides in mycobacteria such asMycobacterium avium. In this study, we identified four genes (gtf1,gtf2,gtf3, andgtf4) in the genome ofMycobacterium smegmatis. These genes were independently inactivated by homologous recombination inM. smegmatis, and the structures of GPLs from each gene disruptant were analyzed. Thin-layer chromatography, gas chromatography-mass spectrometry, and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry analyses revealed that the mutants Δgtf1 and Δgtf2 accumulated the fatty acyl-tetrapeptide core havingO-methyl-rhamnose and 6-deoxy-talose as sugar residues, respectively. The mutant Δgtf4 possessed the same GPLs as the wild type, whereas the mutant Δgtf3 lacked two minor GPLs, consisting of 3-O-methyl-rhamnose attached toO-methyl-rhamnose of the fatty acyl-tetrapeptide core. These results indicate that thegtf1andgtf2genes are responsible for the early glycosylation steps of GPL biosynthesis and thegtf3gene is involved in transferring a rhamnose residue not to 6-deoxy-talose but to anO-methyl-rhamnose residue. Moreover, a complementation experiment showed thatM. avium gtfAandgtfB, which are deduced glycosyltransferase genes of GPL biosynthesis, restore complete GPL production in the mutants Δgtf1 and Δgtf2, respectively. Our findings propose that bothM. smegmatisandM. aviumhave the common glycosylation pathway in the early steps of GPL biosynthesis but differ at the later stages.
Association of Herpesvirus Saimiri Tip with Lipid Raft Is Essential for Downregulation of T-Cell Receptor and CD4 Coreceptor
Authors: Cho Nam-Hyuk , Kingston Dior , Chang Heesoon , Kwon Eun-Kyung , Kim Jo-Min , Lee Jung Hee , Chu Hyuk , Choi Myung-Sik , Kim Ik-Sang , Jung Jae Ung 
Published: December 2005

ABSTRACT
Lipid rafts are membrane microdomains that are proposed to function as platforms for both receptor signaling and trafficking. Our previous studies have demonstrated that Tip of herpesvirus saimiri (HVS), which is a T-lymphotropic tumor virus, is constitutively targeted to lipid rafts and interacts with cellular Lck tyrosine kinase and p80 WD repeat-containing endosomal protein. Through the interactions with Lck and p80, HVS Tip modulates diverse T-cell functions, which leads to the downregulation of T-cell receptor (TCR) and CD4 coreceptor surface expression, the inhibition of TCR signal transduction, and the activation of STAT3 transcription factor. In this study, we investigated the functional significance of Tip association with lipid rafts. We found that Tip expression remarkably increased lipid raft fractions in human T cells by enhancing the recruitment of lipid raft-resident proteins. Genetic analysis showed that the carboxyl-terminal transmembrane, but not p80 and Lck interaction, of Tip was required for the lipid raft localization and that lipid raft localization of Tip was necessary for the efficient downregulation of TCR and CD4 surface expression. Correlated with this, treatment with Filipin III, a lipid raft-disrupting agent, effectively reversed the downregulation of CD3 and CD4 surface expression induced by Tip. On the other hand, Tip mutants that were no longer present in lipid rafts were still capable of inhibiting TCR signaling and activating STAT3 transcription factor activity as efficiently as wild-type (wt) Tip. These results indicate that the association of Tip with lipid rafts is essential for the downregulation of TCR and CD4 surface expression but not for the inhibition of TCR signal transduction and the activation of STAT3 transcription factor. These results also suggest that the signaling and targeting activities of HVS Tip rely on functionally and genetically separable mechanisms, which may independently modulate T-cell function for viral persistence or pathogenesis.
CD8+T Cells Require Perforin To Clear West Nile Virus from Infected Neurons
Authors: Shrestha Bimmi , Samuel Melanie A. , Diamond Michael S. 
Published: December 2005

ABSTRACTInjury to neurons after West Nile virus (WNV) infection is believed to occur because of viral and host immune-mediated effects. Previously, we demonstrated that CD8+T cells are required for the resolution of WNV infection in the central nervous system (CNS). CD8+T cells can control infection by producing antiviral cytokines (e.g., gamma interferon or tumor necrosis factor alpha) or by triggering death of infected cells through perforin- or Fas ligand-dependent pathways. Here, we directly evaluated the role of perforin in controlling infection of a lineage I New York isolate of WNV in mice. A genetic deficiency of perforin molecules resulted in higher viral burden in the CNS and increased mortality after WNV infection. In the few perforin-deficient mice that survived initial challenge, viral persistence was observed in the CNS for several weeks. CD8+T cells required perforin to control WNV infection as adoptive transfer of WNV-primed wild-type but not perforin-deficient CD8+T cells greatly reduced infection in the brain and spinal cord and enhanced survival of CD8-deficient mice. Analogous results were obtained when wild-type or perforin-deficient CD8+T cells were added to congenic primary cortical neuron cultures. Taken together, our data suggest that despite the risk of immunopathogenesis, CD8+T cells use a perforin-dependent mechanism to clear WNV from infected neurons.
Gamma Interferon Blocks Gammaherpesvirus Reactivation from Latency
Authors: Steed Ashley L. , Barton Erik S. , Tibbetts Scott A. , Popkin Daniel L. , Lutzke Mary L. , Rochford Rosemary , Virgin Herbert W. 
Published: December 2005

ABSTRACTEstablishment of latent infection and reactivation from latency are critical aspects of herpesvirus infection and pathogenesis. Interfering with either of these steps in the herpesvirus life cycle may offer a novel strategy for controlling herpesvirus infection and associated disease pathogenesis. Prior studies show that mice deficient in gamma interferon (IFN-γ) or the IFN-γ receptor have elevated numbers of cells reactivating from murine gammaherpesvirus 68 (γHV68) latency, produce infectious virus after the establishment of latency, and develop large-vessel vasculitis. Here, we demonstrate that IFN-γ is a powerful inhibitor of reactivation of γHV68 from latency in tissue culture. In vivo, IFN-γ controls viral gene expression during latency. Importantly, depletion of IFN-γ in latently infected mice results in an increased frequency of cells reactivating virus. This demonstrates that IFN-γ is important for immune surveillance that limits reactivation of γHV68 from latency.
The Pseudorabies Virus VP1/2 Tegument Protein Is Required for Intracellular Capsid Transport
Authors: Luxton G. W. Gant , Lee Joy I-Hsuan , Haverlock-Moyns Sarah , Schober Joseph Martin , Smith Gregory Allan 
Published: December 2005

ABSTRACT
Transport of capsids in cells is critical to alphaherpesvirus infection and pathogenesis; however, viral factors required for transport have yet to be identified. Here we provide a detailed examination of capsid dynamics during the egress phase of infection in Vero cells infected with pseudorabies virus. We demonstrate that the VP1/2 tegument protein is required for processive microtubule-based transport of capsids in the cytoplasm. A second tegument protein that binds to VP1/2, UL37, was necessary for wild-type transport but was not essential for this process. Both proteins were also required for efficient nuclear egress of capsids to the cytoplasm.
Changes in Soluble Factor-Mediated CD8+Cell-Derived Antiviral Activity in Cynomolgus Macaques Infected with Simian Immunodeficiency Virus SIVmac251: Relationship to Biological Markers of Progression
Authors: Dioszeghy Vincent , Benlhassan-Chahour Kadija , Delache Benoit , Dereuddre-Bosquet Nathalie , Aubenque Celine , Gras Gabriel , Le Grand Roger , Vaslin Bruno 
Published: December 2005

ABSTRACTCross-sectional studies have shown that the capacity of CD8+cells from human immunodeficiency virus (HIV)-infected patients and simian immunodeficiency virus (SIV) SIVmac-infected macaques to suppress the replication of human and simian immunodeficiency viruses in vitro depends on the clinical stage of disease, but little is known about changes in this antiviral activity over time in individual HIV-infected patients or SIV-infected macaques. We assessed changes in the soluble factor-mediated noncytolytic antiviral activity of CD8+cells over time in eight cynomolgus macaques infected with SIVmac251 to determine the pathophysiological role of this activity. CD8+cell-associated antiviral activity increased rapidly in the first week after viral inoculation and remained detectable during the early phase of infection. The net increase in antiviral activity of CD8+cells was correlated with plasma viral load throughout the 15 months of follow-up. CD8+cells gradually lost their antiviral activity over time and acquired virus replication-enhancing capacity. Levels of antiviral activity correlated with CD4+T-cell counts after viral set point. Concentrations of β-chemokines and interleukin-16 in CD8+cell supernatants were not correlated with this antiviral activity, and α-defensins were not detected. The soluble factor-mediated antiviral activity of CD8+cells was neither cytolytic nor restricted to major histocompatibility complex. This longitudinal study strongly suggests that the increase in noncytolytic antiviral activity from baseline and the maintenance of this increase over time in cynomolgus macaques depend on both viral replication and CD4+T cells.
Mechanism of Telomerase Activation by v-Rel and Its Contribution to Transformation
Authors: Hrdličková Radmila , Nehyba Jiří , Liss Andrew S. , Bose Henry R. 
Published: December 2005

ABSTRACT
Telomerase
is activated during the transformation of lymphoid cells and
fibroblasts by v-Rel, the oncogenic member of the Rel/NF-κB
family of transcription factors. v-Rel-transformed cell lines have
longer telomeres than untransformed chicken lymphoid cells and have
high levels of telomerase activity. v-Rel-mediated activation of
telomerase is achieved by multiple mechanisms. The expression of the
gene encoding the catalytic subunit of telomerase (TERT) was directly
upregulated by v-Rel. Moreover, the expression of v-Rel altered the
ratio of alternatively spliced and full-length TERT transcripts in
favor of the full-length forms. The activation of telomerase by v-Rel
in lymphocytes was also accompanied by inactivation of nuclear
inhibitors. The inhibition of telomerase activity in v-Rel-transformed
cell lines led to apoptosis within 24 h. The expression of
v-Rel in a macrophage cell line resulted in elevated levels of reactive
oxygen species (ROS), increased telomerase activity, and increased
sensitivity to telomerase inhibitors. In contrast, the ectopic
expression of TERT decreased the extent of apoptosis induced by ROS.
The activation of telomerase by v-Rel may, therefore, partially protect
the transformed cells from apoptosis induced by
ROS.
Expanded Tropism and Altered Activation of a Retroviral Glycoprotein Resistant to an Entry Inhibitor Peptide
Authors: Amberg Sean M. , Netter Robert C. , Simmons Graham , Bates Paul 
Published: December 2005

ABSTRACT

The envelope of class I viruses can be a target for potent viral inhibitors, such as the human immunodeficiency virus type 1 (HIV-1) inhibitor enfuvirtide, which are derived from the C-terminal heptad repeat (HR2) of the transmembrane (TM) subunit. Resistance to an HR2-based peptide inhibitor of a model retrovirus, subgroup A of the
Avian Sarcoma and Leukosis Virus
genus (ASLV-A), was studied by examining mutants derived by viral passage in the presence of inhibitor. Variants with reduced sensitivity to inhibitor were readily selected in vitro. Sensitivity determinants were identified for 13 different isolates, all of which mapped to the TM subunit. These determinants were identified in two regions: (i) the N-terminal heptad repeat (HR1) and (ii) the N-terminal segment of TM, between the subunit cleavage site and the fusion peptide. The latter class of mutants identified a region outside of the predicted HR2-binding site that can significantly alter sensitivity to inhibitor. A subset of the HR1 mutants displayed the unanticipated ability to infect nonavian cells. This expanded tropism was associated with increased efficiency of envelope triggering by soluble receptor at low temperatures, as measured by protease sensitivity of the surface subunit (SU) of envelope. In addition, expanded tropism was linked for the most readily triggered mutants with increased sensitivity to neutralization by SU-specific antiserum. These observations depict a class of HR2 peptide-selected mutations with a reduced activation threshold, thereby allowing the utilization of alternative receptors for viral entry.
Cytokine Responses in Gnotobiotic Pigs after Infection with Virulent or Attenuated Human Rotavirus
Authors: Azevedo M. S. P. , Yuan L. , Pouly S. , Gonzales A. M. , Jeong K. I. , Nguyen T. V. , Saif L. J. 
Published: December 2005

ABSTRACTTo understand the role of cytokines during rotavirus infection, we assessed the kinetics of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) (proinflammatory), IL-12 (Th1 inducer), gamma interferon (IFN-γ) (Th1), IL-4 and IL-10 (Th2), and transforming growth factor β (Th3) cytokine responses by enzyme-linked immunosorbent assay in serum and intestinal contents of neonatal gnotobiotic pigs and IL-12, IFN-γ, IL-4, and IL-10 cytokine-secreting cell (CSC) responses of mononuclear cells from ileum, spleen, and blood by ELISPOT. Pigs received the virulent Wa P1A[8]G1 strain of human rotavirus (HRV) (VirHRV), attenuated Wa HRV (AttHRV), or mock (controls). The TNF-α levels peaked earlier and remained elevated in serum of the VirHRV group but peaked later in the AttHRV group. In serum, IL-6 was significantly elevated at postinoculation day (PID) 1 in the VirHRV group and at PID 3 in both HRV groups. The IL-12 was detected in serum of all pigs including controls with significantly elevated peaks in both HRV-infected groups, indicating a role for IL-12 in the induction of immune responses to rotavirus infection. Only low and transient IFN-γ responses occurred in serum and intestinal contents of the AttHRV-infected pigs, compared to significantly higher and prolonged IFN-γ responses in the VirHRV-infected pigs. This observation coincides with the diarrhea and viremia induced by VirHRV. The number of IFN-γ-secreting cells was significantly higher in the ileum of the VirHRV group than in that of the controls. The number of IL-4 CSCs was significantly higher in ileum of both HRV groups than in that of the controls. Significantly higher levels of IL-10 in the serum occurred early in the VirHRV group, compared to lower levels in the AttHRV group. However, the number of IL-10 CSCs was significantly higher later in ileum and spleen of the AttHRV than in the VirHRV group, suggesting a delayed initiation of a Th2 response induced by AttHRV. A significantly higher percentage of pigs had IFN-γ and IL-10 responses in serum after VirHRV infection than after AttHRV infection or in controls. These data indicate a balanced Th1/Th2 response during rotavirus infection, with higher cytokine levels early after infection with VirHRV compared to that with AttHRV. Mapping the kinetics and patterns of cytokine responses after rotavirus infection has important implications for induction of protective immunity by HRV vaccines. Higher protection rates may be associated with more balanced Th1- and Th2-type responses, but induction of higher earlier IFN-γ (Th1) and proinflammatory cytokines triggered by VirHRV may also play an important role in the higher intestinal immunoglobulin A responses and protection rates induced by VirHRV.
Role of the Mitochondrial Signaling Pathway in Murine Coronavirus-Induced Oligodendrocyte Apoptosis
Authors: Liu Yin , Pu Yinghui , Zhang Xuming 
Published: December 2005

ABSTRACT

A previous study demonstrated that infection of rat oligodendrocytes by mouse hepatitis virus (MHV) resulted in apoptosis, which is caspase dependent (Y. Liu, Y. Cai, and X. Zhang, J. Virol.
77:
11952-11963, 2003). Here we determined the involvement of the mitochondrial pathway in MHV-induced oligodendrocyte apoptosis. We found that caspase-9 activity was 12-fold higher in virus-infected cells than in mock-infected cells at 24 h postinfection (p.i.). Pretreatment of cells with a caspase-9 inhibitor completely blocked caspase-9 activation and partially inhibited the apoptosis mediated by MHV infection. Analyses of cytochrome
c
release further revealed an activation of the mitochondrial apoptotic pathway. Stable overexpression of the two antiapoptotic proteins Bcl-2 and Bcl-xL significantly, though only partially, blocked apoptosis, suggesting that activation of the mitochondrial pathway is partially responsible for the apoptosis. To identify upstream signals, we determined caspase-8 activity, cleavage of Bid, and expression of Bax and Bad by Western blotting. We found a drastic increase in caspase-8 activity and cleavage of Bid at 24 h p.i. in virus-infected cells, suggesting that Bid may serve as a messenger to relay the signals from caspase-8 to mitochondria. However, treatment with a caspase-8 inhibitor only slightly blocked cytochrome
c
release from the mitochondria. Furthermore, we found that Bax but not Bad was significantly increased at 12 h p.i. in cells infected with both live and UV-inactivated viruses and that Bax activation was partially blocked by treatment with the caspase-8 inhibitor. These results thus establish the involvement of the mitochondrial pathway in MHV-induced oligodendrocyte apoptosis.
Hepatitis C Virus Subgenomic Replicon Requires an Active NS3 RNA Helicase
Authors: Lam Angela M. I. , Frick David N. 
Published: December 2005

ABSTRACT
Mutations were introduced into the NS3 helicase region of a hepatitis C virus (HCV) Con1 subgenomic replicon to ascertain the role of the helicase in viral replication. One new replicon lacked two-thirds of the NS3 helicase (Δhel), and six others contained one of the following six amino acid substitutions in NS3: R393A, F438A, T450I, E493K, W501A, and W501F. It has been previously reported that purified R393A, F438A, and W501A HCV helicase proteins do not unwind RNA but unwind DNA, bind RNA, and hydrolyze ATP. On the other hand, previous data suggest that a W501F protein retains most of its unwinding abilities and that purified T450I and E493K HCV helicase proteins have enhanced unwinding abilities. In a hepatoma cell line that has been cured of HCV replicons using interferon, the T450I and W501F replicons synthesized both negative-sense and positive-sense viral RNA and formed colonies after selection with similar efficiencies as the parent replicon. However, the Δhel, R393A, F438A, and W501A replicons encoded and processed an HCV polyprotein but did not synthesize additional viral RNA or form colonies. Surprisingly the same phenotype was seen for the E493K replicon. The inability of the E493K replicon to replicate might point to a role of pH in viral replication because a previous analysis has shown that, unlike the wild-type NS3 protein, the helicase activity of an E493K protein is not sensitive to pH changes. These results demonstrate that the RNA-unwinding activity of the HCV NS3 helicase is needed for RNA replication.