bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feline Leukemia Virus Long Terminal Repeat Activates Collagenase IV Gene Expression through AP-1
Authors: Ghosh Sajal K. , Faller Douglas V. 
Published: December 2019

ABSTRACTLeukemia and lymphoma induced by feline leukemia viruses (FeLVs) are the commonest forms of illness in domestic cats. These viruses do not contain oncogenes, and the source of their pathogenic activity is not clearly understood. Mechanisms involving proto-oncogene activation subsequent to proviral integration and/or development of recombinant viruses with enhanced replication properties are thought to play an important role in their disease pathogenesis. In addition, the long terminal repeat (LTR) regions of these viruses have been shown to be important determinants for pathogenicity and tissue specificity, by virtue of their ability to interact with various transcription factors. Previously, we have shown that, in the case of Moloney murine leukemia virus, the U3 region of the LTR independently induces transcriptional activation of specific cellular genes through an LTR-generated RNA transcript (S. Y. Choi and D. V. Faller, J. Biol. Chem. 269:19691–19694, 1994; S.-Y. Choi and D. V. Faller, J. Virol. 69:7054–7060, 1995). In this report, we show that the U3 region of exogenous FeLV LTRs can induce transcription from collagenase IV (matrix metalloproteinase 9) and monocyte chemotactic protein 1 (MCP-1) promoters up to 12-fold. We also show that AP-1 DNA-binding activity and transcriptional activity are strongly induced in cells expressing FeLV LTRs and that LTR-specific RNA transcripts are generated in those cells. Activation of mitogen-activated protein kinase kinases 1 and 2 (MEK1 and -2) by the LTR is an intermediate step in the FeLV LTR-mediated induction of AP-1 activity. These findings thus suggest that the LTRs of FeLVs can independently activate transcription of specific cellular genes. This LTR-mediated cellular gene transactivation may play an important role in tumorigenesis or preleukemic states and may be a generalizable activity of leukemia-inducing retroviruses.
Anti-Rex Aptamers as Mimics of the Rex-Binding Element
Authors: Baskerville Scott , Zapp Maria , Ellington Andrew D. 
Published: December 2019

ABSTRACT
RNA molecules that bind tightly and specifically to a Rex fusion protein have been isolated from a conformationally constrained pool of random sequence RNAs. The anti-Rex aptamers effectively mimic several features of the wild-type Rex-binding element (XBE). The highest-affinity aptamers effectively compete with the wild-type XBE for binding to the RNA-binding domain of Rex, an arginine-rich motif (ARM), but do not bind to the functionally analogous Rev protein or its ARM. However, characteristic sequence and structural motifs found in some of the anti-Rex aptamers may provide insights into how the Rex protein can interact with other viral RNAs, such as the Rev-responsive element. The anti-Rex aptamers can functionally substitute for the XBE in vivo, a result which supports a previously proposed model for mRNA transport in which the viral genome serves as a platform for assembling a nucleoprotein complex that can co-opt the cellular transport apparatus. Overall, these studies suggest that anti-Rex aptamers may serve as RNA decoys of the Rex protein.
Visualization of Alternative Epstein-Barr Virus Expression Programs by Fluorescent In Situ Hybridization at the Cell Level
Authors: Szeles Anna , Falk Kerstin I. , Imreh Stephan , Klein George 
Published: December 2019

ABSTRACT

Epstein-Barr virus (EBV) transforms human B lymphocytes into immortalized lymphoblastoid cell lines (LCLs). They regularly express six virally encoded nuclear proteins (EBNA1 to EBNA6) and three membrane proteins (LMP1, LMP2A, and LMP2B). In contrast, EBV-carrying Burkitt lymphoma (BL) cells in vivo and derived type I cell lines that maintain the BL phenotype express only EBNA1. During prolonged in vitro culturing, most EBV-carrying BL lines drift toward a more immunoblastic (type II or III) phenotype. Their viral antigen expression is upregulated in parallel. We have used fluorescent in situ hybridization to visualize viral transcripts in type I and III BL lines and LCLs. In type I cells, EBNA1 is encoded by a monocistronic message that originates from the Qp promoter. In type III cells, the EBNA1 transcript is spliced from a giant polycistronic message that originates from one of several alternative Wp or Cp promoters and encodes all six EBNAs. We have obtained a “track” signal with a
Bam
HI W DNA probe that could hybridize with the polycistronic but not with the monocistronic message in two type III BL lines (Namalwa-Cl8 and MUTU III) and three LCLs (LCL IB4-D, LCL-970402, and IARC-171). A
Bam
HI K probe that can hybridize to both the monocistronic and the polycistronic message visualized the same pattern in the type III BLs and the LCLs as the
Bam
HI W probe. A positive signal was obtained with the
Bam
HI K but not the
Bam
HI W probe in the type I BL lines MUTU I and Rael. The RNA track method can thus distinguish between cells that use a type III and those that use a type I program. The former cells hybridize with both the W and the K probes, but the latter cells hybridize with only the K probe. Our findings may open the way for studies of the important but still unanswered question of whether cells with type I latency arise from immunoblasts with a full type III program or are generated by a separate pathway during primary infection.
Human Memory Cytotoxic T-Lymphocyte (CTL) Responses to Hantaan Virus Infection: Identification of Virus-Specific and Cross-Reactive CD8+CTL Epitopes on Nucleocapsid Protein
Authors: Van Epps Heather L. , Schmaljohn Connie S. , Ennis Francis A. 
Published: December 2019

ABSTRACTHantaan virus, the prototypic member of theHantavirusgenus, causes hemorrhagic fever with renal syndrome in humans. We examined the human memory T-lymphocyte responses of three donors who had previous laboratory-acquired infections with Hantaan virus. We demonstrated virus-specific responses in bulk cultures of peripheral blood mononuclear cells (PBMC) from all donors. Bulk T-cell responses were directed against either Hantaan virus nucleocapsid (N) or G1 protein, and these responses varied between donors. We established both CD4+and CD8+N-specific cell lines from two donors and CD4+G1-specific cell lines from a third donor. All CD8+cytotoxic T-lymphocyte (CTL) lines recognized one of two epitopes on the nucleocapsid protein: one epitope spanning amino acids 12 to 20 and the other spanning amino acids 421 to 429. The CTL lines specific for amino acids 12 to 20 were restricted by HLA B51, and those specific for amino acids 421 to 429 were restricted by HLA A1. The N-specific CTL lines isolated from these two donors included both Hantaan virus-specific CTLs and hantavirus cross-reactive CTLs. Responses to both epitopes are detectable in short-term bulk cultures of PBMC from one donor, and precursor frequency analysis confirms that CTLs specific for these epitopes are present at relatively high precursor frequencies in the peripheral T-cell pool. These data suggest that infection with Hantaan virus results in the generation of CTL to limited epitopes on the nucleocapsid protein and that infection also results in the generation of cross-reactive T-cell responses to distantly related hantaviruses which cause the distinct hantavirus pulmonary syndrome. This is the first demonstration of human T-lymphocyte responses to Hantaan virus.
Translation Elongation Factor 1-Alpha Interacts Specifically with the Human Immunodeficiency Virus Type 1 Gag Polyprotein
Authors: Cimarelli Andrea , Luban Jeremy 
Published: December 2019

ABSTRACT

Human immunodeficiency virus type 1 (HIV-1)
gag
-encoded proteins play key functions at almost all stages of the viral life cycle. Since these functions may require association with cellular factors, the HIV-1 matrix protein (MA) was used as bait in a yeast two-hybrid screen to identify MA-interacting proteins. MA was found to interact with elongation factor 1-alpha (EF1α), an essential component of the translation machinery that delivers aminoacyl-tRNA to ribosomes. EF1α was then shown to bind the entire HIV-1 Gag polyprotein. This interaction is mediated not only by MA, but also by the nucleocapsid domain, which provides a second, independent EF1α-binding site on the Gag polyprotein. EF1α is incorporated within HIV-1 virion membranes, where it is cleaved by the viral protease and protected from digestion by exogenously added subtilisin. The specificity of the interaction is demonstrated by the fact that EF1α does not bind to nonlentiviral MAs and does not associate with Moloney murine leukemia virus virions. The Gag-EF1α interaction appears to be mediated by RNA, in that basic residues in MA and NC are required for binding to EF1α, RNase disrupts the interaction, and a Gag mutant with undetectable EF1α-binding activity is impaired in its ability to associate with tRNA in cells. Finally, the interaction between MA and EF1α impairs translation in vitro, a result consistent with a previously proposed model in which inhibition of translation by the accumulation of Gag serves to release viral RNA from polysomes, permitting the RNA to be packaged into nascent virions.
Cell Cycle- and Vpr-Mediated Regulation of Human Immunodeficiency Virus Type 1 Expression in Primary and Transformed T-Cell Lines
Authors: Gummuluru Suryaram , Emerman Michael 
Published: December 2019

ABSTRACT

Viral protein R (Vpr) of human immunodeficiency virus type 1 (HIV-1) transiently arrests cells in the G
2
phase of the cell cycle and is a weak transcriptional transactivator. We found that Vpr increased HIV-1 long terminal repeat (LTR) activity in all cells examined but, when expressed at high levels, decreased HIV-1 LTR expression due to cytotoxic effects. Moreover, Vpr-mediated enhancement of HIV-1 LTR-driven transcription was observed in cycling primary human CD4
+
T cells but not in terminally differentiated, noncycling primary human macrophages. In single-round infection experiments using primary human CD4
+
T cells, proviral clones expressing either wild-type Vpr or Vpr mutants that retained the ability to cause a G
2
arrest replicated to higher levels than proviruses lacking Vpr or expressing mutants of Vpr that did not cause an arrest. In support of the hypothesis that enhancement of HIV-1 LTR transcription by Vpr is an indirect effect of the ability of Vpr to delay cells in G
2
, counterflow centrifugal elutriation of cells into different phases of the cell cycle demonstrated that HIV-1 LTR expression was highest in G
2
. Finally, the ability of Vpr to upregulate viral transcription was dependent on a minimal promoter containing a functional TATA box and an enhancer.
Human and Rodent Transcription Elongation Factor P-TEFb: Interactions with Human Immunodeficiency Virus Type 1 Tat and Carboxy-Terminal Domain Substrate
Authors: Ramanathan Y. , Reza Syed M. , Young Tara M. , Mathews Michael B. , Pe’ery Tsafi 
Published: December 2019

ABSTRACT
The human immunodeficiency virus type 1 transcriptional regulator Tat increases the efficiency of elongation, and complexes containing the cellular kinase CDK9 have been implicated in this process. CDK9 is part of the Tat-associated kinase TAK and of the elongation factor P-TEFb (positive transcription elongation factor-b), which consists minimally of CDK9 and cyclin T. TAK and P-TEFb are both able to phosphorylate the carboxy-terminal domain (CTD) of RNA polymerase II, but their relationships to one another and to the stimulation of elongation by Tat are not well characterized. Here we demonstrate that human cyclin T1 (but not cyclin T2) interacts with the activation domain of Tat and is a component of TAK as well as of P-TEFb. Rodent (mouse and Chinese hamster) cyclin T1 is defective in Tat binding and transactivation, but hamster CDK9 interacts with human cyclin T1 to give active TAK in hybrid cells containing human chromosome 12. Although TAK is phosphorylated on both serine and threonine residues, it specifically phosphorylates serine 5 in the CTD heptamer. TAK is found in the nuclear and cytoplasmic fractions of human cells as a large complex (∼950 kDa). Magnesium or zinc ions are required for the association of Tat with the kinase. We suggest a model in which Tat first interacts with P-TEFb to form the TAK complex that engages with TAR RNA and the elongating transcription complex, resulting in hyperphosphorylation of the CTD on serine 5 residues.
Lack of Viral Escape and Defective In Vivo Activation of Human Immunodeficiency Virus Type 1-Specific Cytotoxic T Lymphocytes in Rapidly Progressive Infection
Authors: Hay Christine M. , Ruhl Debbie J. , Basgoz Nesli O. , Wilson Cara C. , Billingsley James M. , DePasquale Maria Pia , D’Aquila Richard T. , Wolinsky Steven M. , Crawford John M. , Montefiori David C. , Walker Bruce D. 
Published: December 2019

ABSTRACTHuman immunodeficiency virus type 1 (HIV-1)-specific immune responses over the course of rapidly progressive infection are not well defined. Detailed longitudinal analyses of neutralizing antibodies, lymphocyte proliferation, in vivo-activated and memory cytotoxic T-lymphocyte (CTL) responses, and viral sequence variation were performed on a patient who presented with acute HIV-1 infection, developed an AIDS-defining illness 13 months later, and died 45 months after presentation. Neutralizing-antibody responses remained weak throughout, and no HIV-1-specific lymphocyte proliferative responses were seen even early in the disease course. Strong in vivo-activated CTL directed against Env and Pol epitopes were present at the time of the initial drop in viremia but were quickly lost. Memory CTL against Env and Pol epitopes were detected throughout the course of infection; however, these CTL were not activated in vivo. Despite an initially narrow CTL response, new epitopes were not targeted as the disease progressed. Viral sequencing showed the emergence of variants within the two targeted CTL epitopes; however, viral variants within the immunodominant Env epitope were well recognized by CTL, and there was no evidence of viral escape from immune system detection within this epitope. These data demonstrate a narrowly directed, static CTL response in a patient with rapidly progressive disease. We also show that disease progression can occur in the presence of persistent memory CTL recognition of autologous epitopes and in the absence of detectable escape from CTL responses, consistent with an in vivo defect in activation of CTL.
Matrix Metalloproteinase 9 Expression Is Induced by Epstein-Barr Virus Latent Membrane Protein 1 C-Terminal Activation Regions 1 and 2
Authors: Takeshita Hajime , Yoshizaki Tomokazu , Miller William E. , Sato Hiroshi , Furukawa Mitsuru , Pagano Joseph S. , Raab-Traub Nancy 
Published: December 2019

ABSTRACTNasopharyngeal carcinoma (NPC), which is closely associated with the Epstein-Barr virus (EBV), is a highly metastatic malignant tumor. An important activity in tumor invasion and metastasis is that of the 92-kDa type IV collagenase or gelatinase, matrix metalloproteinase 9 (MMP-9), which mediates the degradation of the basement membrane and extracellular matrix. The expression of MMP-9 has been shown to be enhanced by the EBV oncoprotein, latent membrane protein 1 (LMP-1). LMP-1, which is expressed in NPC, has two essential signaling domains within the carboxy terminus, termed C-terminal activation regions 1 (CTAR-1) and CTAR-2. This study reveals that either signaling domain can activate the MMP-9 promoter and induce MMP-9 activity; however, LMP-1 deletion mutants lacking either CTAR-1 or CTAR-2 had a decreased ability to induce MMP-9 expression. The deletion of both activation regions completely abolished the induction of MMP-9 activity, while the cotransfection of both the CTAR-1 and CTAR-2 deletion mutants restored MMP-9 activity to levels produced by wild-type LMP-1. The NF-κB and activator protein 1 (AP-1) binding sites in the MMP-9 promoter were essential for the activation of MMP-9 gene expression by both CTAR-1 and CTAR-2. The induction of MMP-9 expression by LMP-1 and both CTAR-1 and CTAR-2 mutants was blocked by the overexpression of IκB. The tumor necrosis factor receptor-associated factor (TRAF) pathway also contributed to the activation of the MMP-9 promoter as shown by the use of TRAF-2 and TRAF-3 dominant-negative constructs. These data indicate that the activation of both the NF-κB and AP-1 pathways by LMP-1, CTAR-1, and CTAR-2 is necessary for the activation of MMP-9 expression. In NPC, LMP-1 may contribute to invasiveness and metastasis through the induction of MMP-9 transcription and enzymatic activity.
Identification of the Immediate-Early Transcripts of Kaposi’s Sarcoma-Associated Herpesvirus
Authors: Zhu Fan Xiu , Cusano Teresa , Yuan Yan 
Published: December 2019

ABSTRACT
In the immediate-early phase of reactivation or primary infection, herpesviruses express a small number of genes without requiring prior viral protein synthesis. Immediate-early genes usually encode regulatory proteins critical for the viral life cycle. Kaposi’s sarcoma-associated herpesvirus (KSHV) gene transcription in the immediate-early stage of viral reactivation was examined by using a chemical induction combined with a gene expression screening method. RNA transcripts from at least four KSHV genomic loci accumulate when latently infected B-lymphoma cells are induced for reactivation in the presence of an inhibitor of protein synthesis (cycloheximide) and thus represent immediate-early class transcripts. Among them, a 3.6-kb mRNA encodes three putative open reading frames (ORFs), namely, ORF50, K8, and K8.2. ORF50 is a homologue of Rta, a transcription activator encoded by Epstein-Barr virus (EBV). The K8 gene codes for a 237-amino-acid protein with a basic-leucine zipper domain near its C terminus and an acidic domain near its N terminus and which closely resembles the ZEBRA protein of EBV and Jun/Fos family proteins. Other immediate-early mRNAs of KSHV include a 1.7-kb mRNA encoding ORF45, a 2.0-kb mRNA encoding ORF K4.2, and a 4.5-kb mRNA. Functional roles of products of these KSHV immediate-early transcripts remain to be studied.
The Versatility of Paramyxovirus RNA Polymerase Stuttering
Authors: Hausmann Stéphane , Garcin Dominique , Delenda Christophe , Kolakofsky Daniel 
Published: December 2019

ABSTRACT

Paramyxoviruses cotranscriptionally edit their P gene mRNAs by expanding the number of Gs of a conserved A
n
G
n
run. Different viruses insert different distributions of guanylates, e.g., Sendai virus inserts a single G, whereas parainfluenza virus type 3 inserts one to six Gs. The sequences conserved at the editing site, as well as the experimental evidence, suggest that the insertions occur by a stuttering process, i.e., by pseudotemplated transcription. The number of times the polymerase “stutters” at the editing site before continuing strictly templated elongation is directed by a
cis
-acting sequence found upstream of the insertions. We have examined the stuttering process during natural virus infections by constructing recombinant Sendai viruses with mutations in their
cis
-acting sequences. We found that the template stutter site is precisely determined (C
1052
) and that a relatively short region (∼6 nucleotides) just upstream of the A
n
G
n
run can modulate the overall frequency of mRNA editing as well as the distribution of the nucleotide insertions. The positions more proximal to the 5′ A
n
G
n
run are the most important in this respect. We also provide evidence that the stability of the mRNA/template hybrid plays a determining role in the overall frequency and range of mRNA editing. When the template U run is extended all the way to the stutter site, adenylates rather than guanylates are added at the editing site and their distribution begins to resemble the polyadenylation associated with mRNA 3′ end formation by the viral polymerase. Our data suggest how paramyxovirus mRNA editing and polyadenylation are related mechanistically and how editing sites may have evolved from poly(A)-termination sites or vice versa.
γδ+T Cells Regulate Major Histocompatibility Complex Class II (IA and IE)-Dependent Susceptibility to Coxsackievirus B3-Induced Autoimmune Myocarditis
Authors: Huber S. A. , Stone J. E. , Wagner D. H. , Kupperman J. , Pfeiffer L. , David C. , O’Brien R. L. , Davis G. S. , Newell M. K. 
Published: December 2019

ABSTRACTCoxsackievirus B3 (CVB3) infection induces myocardial inflammation and myocyte necrosis in some, but not all, strains of mice. C57BL/6 mice, which inherently lack major histocompatibility complex (MHC) class II IE antigen, develop minimal cardiac lesions despite high levels of virus in the heart. The present experiments evaluate the relative roles of class II IA and IE expression on myocarditis susceptibility in four transgenic C57BL/6 mouse strains differing in MHC class II antigen expression. Animals lacking MHC class II IE antigen (C57BL/6 [IA+IE−] and ABo[IA−IE−]) developed minimal cardiac lesions subsequent to infection despite high concentrations of virus in the heart. In contrast, strains expressing IE (ABoEα [IA−IE+] and Bl.Tg.Eα [IA+IE+]) had substantial cardiac injury. Myocarditis susceptibility correlated to a Th1 (gamma interferon-positive) cell response in the spleen, while disease resistance correlated to a preferential Th2 (interleukin-4-positive) phenotype. Vγ/Vδ analysis indicates that distinct subpopulations of γδ+T cells are activated after CVB3 infection of C57BL/6 and Bl.Tg.Eα mice. Depletion of γδ+T cells abrogated myocarditis susceptibility in IE+animals and resulted in a Th1→Th2 phenotype shift. These studies indicate that the MHC class II antigen haplotype controls myocarditis susceptibility, that this control is most likely mediated through the type of γδ T cells activated during CVB3 infection, and finally that different subpopulations of γδ+T cells may either promote or inhibit Th1 cell responses.