bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prominent Amphibian (Xenopus laevis) Tadpole Type III Interferon Response to the Frog Virus 3 Ranavirus
Authors: Grayfer Leon , De Jesús Andino Francisco , Robert Jacques 
Published: February 2015

ABSTRACT

Ranaviruses (
Iridoviridae
) are posing an increasing threat to amphibian populations, with anuran tadpoles being particularly susceptible to these viral infections. Moreover, amphibians are the most basal phylogenetic class of vertebrates known to possess both type I and type III interferon (IFN)-mediated immunity. Moreover, little is known regarding the respective roles of the IFN mediators in amphibian antiviral defenses. Accordingly, we transcriptionally and functionally compared the amphibian
Xenopus laevis
type I (IFN) and III (IFN-λ) IFNs in the context of infections by the ranavirus frog virus 3 (FV3).
X. laevis
IFN and IFN-λ displayed distinct tissue expression profiles. In contrast to our previous findings that
X. laevis
tadpoles exhibit delayed and modest type I IFN responses to FV3 infections compared to the responses of adults, here we report that tadpoles mount timely and robust type III IFN gene responses. Recombinant forms of these cytokines (recombinant
X. laevis
IFN [r
Xl
IFN] and r
Xl
IFN-λ) elicited antiviral gene expression in the kidney-derived A6 cell line as well as in tadpole leukocytes and tissues. However, r
Xl
IFN-λ was less effective than r
Xl
IFN in preventing FV3 replication in A6 cells and tadpoles and inferior at promoting tadpole survival. Intriguingly, FV3 impaired A6 cell and tadpole kidney type III IFN receptor gene expression. Furthermore, in A6 cultures r
Xl
IFN-λ conferred equal or greater protection than r
Xl
IFN against recombinant viruses deficient for the putative immune evasion genes, the viral caspase activation and recruitment domain (vCARD) or a truncated vIF-2α gene. Thus, in contrast to previous assumptions, tadpoles possess intact antiviral defenses reliant on type III IFNs, which are overcome by FV3 pathogens.

IMPORTANCE
Anuran tadpoles, including those of
Xenopus laevis
, are particularly susceptible to infection by ranavirus such as FV3. We investigated the respective roles of
X. laevis
type I and type III interferons (IFN and IFN-λ, respectively) during FV3 infections. Notably, tadpoles mounted timely and more robust IFN-λ gene expression responses to FV3 than adults, contrasting with the poorer tadpole type I IFN responses. However, a recombinant
X. laevis
IFN-λ (r
Xl
IFN-λ) conferred less protection to tadpoles and the A6 cell line than r
Xl
IFN, which may be explained by the FV3 impairment of IFN-λ receptor gene expression. The importance of IFN-λ in tadpole anti-FV3 defenses is underlined by the critical involvement of two putative immune evasion genes in FV3 resistance to IFN- and IFN-λ-mediated responses. These findings challenge the view that tadpoles have defective antiviral immunity and suggest, rather, that their antiviral responses are predominated by IFN-λ responses, which are overcome by FV3.
Oropouche Virus Infection and Pathogenesis Are Restricted by MAVS, IRF-3, IRF-7, and Type I Interferon Signaling Pathways in Nonmyeloid Cells
Authors: Proenca-Modena Jose Luiz , Sesti-Costa Renata , Pinto Amelia K. , Richner Justin M. , Lazear Helen M. , Lucas Tiffany , Hyde Jennifer L. , Diamond Michael S. 
Published: February 2015

ABSTRACT

Oropouche virus (OROV) is a member of the
Orthobunyavirus
genus in the
Bunyaviridae
family and a prominent cause of insect-transmitted viral disease in Central and South America. Despite its clinical relevance, little is known about OROV pathogenesis. To define the host defense pathways that control OROV infection and disease, we evaluated OROV pathogenesis and immune responses in primary cells and mice that were deficient in the RIG-I-like receptor signaling pathway (MDA5, RIG-I, or MAVS), downstream regulatory transcription factors (IRF-3 or IRF-7), beta interferon (IFN-β), or the receptor for type I IFN signaling (IFNAR). OROV replicated to higher levels in primary fibroblasts and dendritic cells lacking MAVS signaling, the transcription factors IRF-3 and IRF-7, or IFNAR than in wild-type (WT) cells. In mice, deletion of IFNAR, MAVS, or IRF-3 and IRF-7 resulted in uncontrolled OROV replication, hypercytokinemia, extensive liver damage, and death, whereas WT congenic animals failed to develop disease. Unexpectedly, mice with a selective deletion of IFNAR on myeloid cells (CD11c Cre
+
Ifnar
f/f
or LysM Cre
+
Ifnar
f/f
) did not sustain enhanced disease with OROV or a selective (flox/flox) deletion La Crosse virus, a closely related encephalitic orthobunyavirus. In bone marrow chimera studies, recipient irradiated
Ifnar
−/−
mice reconstituted with WT hematopoietic cells sustained high levels of OROV replication and liver damage, whereas WT mice reconstituted with
Ifnar
−/−
bone marrow were resistant to disease. Collectively, these results establish a dominant protective role for MAVS, IRF-3 and IRF-7, and IFNAR in restricting OROV infection and tissue injury and suggest that IFN signaling in nonmyeloid cells contributes to the host defense against orthobunyaviruses.

IMPORTANCE
Oropouche virus (OROV) is an emerging arthropod-transmitted orthobunyavirus that causes episodic outbreaks of a debilitating febrile illness in humans in countries of South and Central America. The continued expansion of the range and number of its arthropod vectors increases the likelihood that OROV will spread into new regions. At present, the pathogenesis of OROV in humans or other vertebrate animals remains poorly understood. To define cellular mechanisms of control of OROV infection, we performed infection studies in a series of primary cells and mice that were deficient in key innate immune genes involved in pathogen recognition and control. Our results establish that a MAVS-dependent type I IFN signaling pathway has a dominant role in restricting OROV infection and pathogenesis
in vivo
.
A Role for 3-
O
-Sulfated Heparan Sulfate in Promoting Human Cytomegalovirus Infection in Human Iris Cells
Authors: Baldwin John , Maus Erika , Zanotti Brian , Volin Michael V. , Tandon Ritesh , Shukla Deepak , Tiwari Vaibhav 
Published: February 2015

ABSTRACT

Human cytomegalovirus (HCMV) has emerged as a clinically opportunistic pathogen that targets multiple types of ocular cells and tissues, including the iris region of the uveal tract during anterior uveitis. In this report, we used primary cultures of human iris stroma (HIS) cells derived from human eye donors to investigate HCMV entry. The following lines of evidence suggested the role of 3-
O
-sulfated heparan sulfate (3-
O
S HS) during HCMV-mediated entry and cell-to-cell fusion in HIS cells. First, 3-
O
-sulfotransferase-3 (3-
O
ST-3) expression in HIS cells promoted HCMV internalization, while pretreatment of HIS cells with heparinase enzyme or with anti-3-
O
S HS (G2) peptide significantly reduced the HCMV-mediated formation of plaques/foci. Second, coculture of the HCMV-infected HIS cells with CHO-K1 cells expressing 3-
O
S HS significantly enhanced cell fusion. Finally, a similar trend of enhanced fusion was observed with cells expressing HCMV glycoproteins (gB, gO, and gH-gL) cocultured with 3-
O
S HS cells. Taken together, these results highlight the role of 3-
O
S HS during HCMV plaque formation and cell-to-cell fusion and identify a novel target for future therapeutic interventions.
Cellular STAT3 Functions via PCBP2 To Restrain Epstein-Barr Virus Lytic Activation in B Lymphocytes
Authors: Koganti Siva , Clark Carissa , Zhi Jizu , Li Xiaofan , Chen Emily I. , Chakrabortty Sharmistha , Hill Erik R. , Bhaduri-McIntosh Sumita 
Published: February 2015

ABSTRACT

A major hurdle to killing Epstein-Barr virus (EBV)-infected tumor cells using oncolytic therapy is the presence of a substantial fraction of EBV-infected cells that does not support the lytic phase of EBV despite exposure to lytic cycle-promoting agents. To determine the mechanism(s) underlying this refractory state, we developed a strategy to separate lytic from refractory EBV-positive (EBV
+
) cells. By examining the cellular transcriptome in separated cells, we previously discovered that high levels of host STAT3 (signal transducer and activator of transcription 3) curtail the susceptibility of latently infected cells to lytic cycle activation signals. The goals of the present study were 2-fold: (i) to determine the mechanism of STAT3-mediated resistance to lytic activation and (ii) to exploit our findings to enhance susceptibility to lytic activation. We therefore analyzed our microarray data set, cellular proteomes of separated lytic and refractory cells, and a publically available STAT3 chromatin immunoprecipitation sequencing (ChIP-Seq) data set to identify cellular PCBP2 [poly(C)-binding protein 2], an RNA-binding protein, as a transcriptional target of STAT3 in refractory cells. Using Burkitt lymphoma cells and EBV
+
cell lines from patients with hypomorphic
STAT3
mutations, we demonstrate that single cells expressing high levels of PCBP2 are refractory to spontaneous and induced EBV lytic activation, STAT3 functions via cellular PCBP2 to regulate lytic susceptibility, and suppression of PCBP2 levels is sufficient to increase the number of EBV lytic cells. We expect that these findings and the genome-wide resources that they provide will accelerate our understanding of a longstanding mystery in EBV biology and guide efforts to improve oncolytic therapy for EBV-associated cancers.

IMPORTANCE
Most humans are infected with Epstein-Barr virus (EBV), a cancer-causing virus. While EBV generally persists silently in B lymphocytes, periodic lytic (re)activation of latent virus is central to its life cycle and to most EBV-related diseases. However, a substantial fraction of EBV-infected B cells and tumor cells in a population is refractory to lytic activation. This resistance to lytic activation directly and profoundly impacts viral persistence and the effectiveness of oncolytic therapy for EBV
+
cancers. To identify the mechanisms that underlie susceptibility to EBV lytic activation, we used host gene and protein expression profiling of separated lytic and refractory cells. We find that STAT3, a transcription factor overactive in many cancers, regulates PCBP2, a protein important in RNA biogenesis, to regulate susceptibility to lytic cycle activation signals. These findings advance our understanding of EBV persistence and provide important leads on devising methods to improve viral oncolytic therapies.
Activation of NF-κB by Human Papillomavirus 16 E1 Limits E1-Dependent Viral Replication through Degradation of E1
Authors: Nakahara Tomomi , Tanaka Katsuyuki , Ohno Shin-ichi , Egawa Nagayasu , Yugawa Takashi , Kiyono Tohru 
Published: February 2015

ABSTRACT
NF-κB is a family of transcription factors that regulate gene expression involved in many processes, such as the inflammatory response and cancer progression. Little is known about associations of NF-κB with the human papillomavirus (HPV) life cycle. We have developed a tissue culture system to conditionally induce E1-dependent replication of the human papillomavirus 16 (HPV16) genome in human cervical keratinocytes and found that expression of HPV16 E1, a viral helicase, results in reduction of IκBα and subsequent activation of NF-κB in a manner dependent on helicase activity. Exogenous expression of a degradation-resistant mutant of IκBα, which inhibits the activation of NF-κB, enhanced E1-dependent replication of the viral genome. Wortmannin, a broad inhibitor of phosphoinositide 3-kinases (PI3Ks), and, to a lesser extent, VE-822, an ATR kinase inhibitor, but not KU55933, an ATM kinase inhibitor, suppressed the activation of NF-κB and augmented E1-dependent replication of the HPV16 genome. Interestingly, the enhancement of E1-dependent replication of the viral genome was associated with increased stability of E1 in the presence of wortmannin as well as the IκBα mutant. Collectively, we propose that expression of E1 induces NF-κB activation at least in part through the ATR-dependent DNA damage response and that NF-κB in turn limits E1-dependent replication of HPV16 through degradation of E1, so that E1 and NF-κB may constitute a negative feedback loop.

IMPORTANCE
A major risk factor in human papillomavirus (HPV)-associated cancers is persistent infection with high-risk HPVs. To eradicate viruses from infected tissue, it is important to understand molecular mechanisms underlying the establishment and maintenance of persistent infection. In this study, we obtained evidence that human papillomavirus 16 (HPV16) E1, a viral DNA helicase essential for amplification of the viral genomes, induces NF-κB activation and that this limits E1-dependent genome replication of HPV16. These results suggest that NF-κB mediates a negative feedback loop to regulate HPV replication and that this feedback loop could be associated with control of the viral copy numbers. We could thus show for the first time that NF-κB activity is involved in the establishment and maintenance of persistent HPV infection.
Human Papillomavirus 16 Oncoprotein Expression Is Controlled by the Cellular Splicing Factor SRSF2 (SC35)
Authors: McFarlane Melanie , MacDonald Alasdair I. , Stevenson Andrew , Graham Sheila V. 
Published: February 2015

ABSTRACT

High-risk human papillomaviruses (HR-HPV) cause anogenital cancers, including cervical cancer, and head and neck cancers. Human papillomavirus 16 (HPV16) is the most prevalent HR-HPV. HPV oncogenesis is driven by two viral oncoproteins, E6 and E7, which are expressed through alternative splicing of a polycistronic RNA to yield four major splice isoforms (E6 full length, E6*I, E6*II, E6*X). The production of multiple mRNA isoforms from a single gene is controlled by serine/arginine-rich splicing factors (SRSFs), and HPV16 infection induces overexpression of a subset of these, SRSFs 1, 2, and 3. In this study, we examined whether these proteins could control HPV16 oncoprotein expression. Small interfering RNA (siRNA) depletion experiments revealed that SRSF1 did not affect oncoprotein RNA levels. While SRSF3 knockdown caused some reduction in E6E7 expression, depletion of SRSF2 resulted in a significant loss of E6E7 RNAs, resulting in reduced levels of the E6-regulated p53 proteins and E7 oncoprotein itself. SRSF2 contributed to the tumor phenotype of HPV16-positive cervical cancer cells, as its depletion resulted in decreased cell proliferation, reduced colony formation, and increased apoptosis. SRSF2 did not affect transcription from the P
97
promoter that controls viral oncoprotein expression. Rather, RNA decay experiments showed that SRSF2 is required to maintain stability of E6E7 mRNAs. These data show that SRSF2 is a key regulator of HPV16 oncoprotein expression and cervical tumor maintenance.

IMPORTANCE
Expression of the HPV16 oncoproteins E7 and E6 drives HPV-associated tumor formation. Although increased transcription may yield increased levels of E6E7 mRNAs, it is known that the RNAs can have increased stability upon integration into the host genome. SR splicing factors (SRSFs) control splicing but can also control other events in the RNA life cycle, including RNA stability. Previously, we demonstrated increased levels of SRSFs 1, 2, and 3 during cervical tumor progression. Now we show that SRSF2 is required for expression of E6E7 mRNAs in cervical tumor but not nontumor cells and may act by inhibiting their decay. SRSF2 depletion in W12 tumor cells resulted in increased apoptosis, decreased proliferation, and decreased colony formation, suggesting that SRSF2 has oncogenic functions in cervical tumor progression. SRSF function can be targeted by known drugs that inhibit SRSF phosphorylation, suggesting a possible new avenue in abrogating HPV oncoprotein activity.
The Cellobiose Sensor CebR Is the Gatekeeper of Streptomyces scabies Pathogenicity
Authors: Francis Isolde M. , Jourdan Samuel , Fanara Steven , Loria Rosemary , Rigali Sébastien 
Published: February 2015

ABSTRACTA relatively small number of species in the large genus Streptomyces are pathogenic; the best characterized of these is Streptomyces scabies. The pathogenicity of S. scabies strains is dependent on the production of the nitrated diketopiperazine thaxtomin A, which is a potent plant cellulose synthesis inhibitor. Much is known about the genetic loci associated with plant virulence; however, the molecular mechanisms by which S. scabies triggers expression of thaxtomin biosynthetic genes, beyond the pathway-specific activator TxtR, are not well understood. In this study, we demonstrate that binding sites for the cellulose utilization repressor CebR occur and function within the thaxtomin biosynthetic cluster. This was an unexpected result, as CebR is devoted to primary metabolism and nutritive functions in nonpathogenic streptomycetes. In S. scabies, cellobiose and cellotriose inhibit the DNA-binding ability of CebR, leading to an increased expression of the thaxtomin biosynthetic and regulatory genestxtA,txtB, andtxtR. Deletion ofcebRresults in constitutive thaxtomin A production and hypervirulence of S. scabies. The pathogenicity of S. scabies is thus under dual direct positive and negative transcriptional control where CebR is the cellobiose-sensing key that locks the expression oftxtR, the key necessary to unlock the production of the phytotoxin. Interestingly, CebR-binding sites also lie upstream of and within the thaxtomin biosynthetic clusters in Streptomyces turgidiscabies and Streptomyces acidiscabies, suggesting that CebR is most likely an important regulator of virulence in these plant-pathogenic species as well.IMPORTANCEWhat makes a microorganism pathogenic is not limited to the genes acquired for virulence. Using the main causative agent of scab lesions on root and tuber crops as an example, our work identified the subtle but essential genetic changes that generate thecis-acting elements necessary for proper timing of the expression of the cluster of genes responsible for the biosynthesis of thaxtomin A, the primary virulence factor in plant-pathogenic streptomycetes. These data illustrate a situation in which a regulator associated with primary metabolism in nonpathogens, CebR, has been coopted as a master regulator of virulence in pathogenic species. Furthermore, the manipulation of CebR-mediated control of thaxtomin production will facilitate overproduction of this natural and biodegradable herbicide for commercial purposes. Our work thus provides a concrete example of how a strictly theoretical and computational work was able to elucidate a regulatory mechanism associated with the virulence of a plant pathogen and to generate solutions to purely agro-industrial concerns.
Positioning the Flagellum at the Center of a Dividing Cell To Combine Bacterial Division with Magnetic Polarity
Authors: Lefèvre Christopher T. , Bennet Mathieu , Klumpp Stefan , Faivre Damien 
Published: February 2015

ABSTRACT

Faithful replication of all structural features is a
sine qua non
condition for the success of bacterial reproduction by binary fission. For some species, a key challenge is to replicate and organize structures with multiple polarities. Polarly flagellated magnetotactic bacteria are the prime example of organisms dealing with such a dichotomy; they have the challenge of bequeathing two types of polarities to their daughter cells: magnetic and flagellar polarities. Indeed, these microorganisms align and move in the Earth's magnetic field using an intracellular chain of nano-magnets that imparts a magnetic dipole to the cell. The paradox is that, after division occurs in cells, if the new flagellum is positioned opposite to the old pole devoid of a flagellum during cell division, the two daughter cells will have opposite magnetic polarities with respect to the positions of their flagella. Here we show that magnetotactic bacteria of the class
Gammaproteobacteria
pragmatically solve this problem by synthesizing a new flagellum at the division site. In addition, we model this particular structural inheritance during cell division. This finding opens up new questions regarding the molecular aspects of the new division mechanism, the way other polarly flagellated magnetotactic bacteria control the rotational direction of their flagella, and the positioning of organelles.

IMPORTANCE
Magnetotactic bacteria produce chains of magnetic nanoparticles that endow the cells with a magnetic dipole, a “compass” used for navigation. This feature, however, also drastically complicates cellular division in the case of polarly flagellated bacteria. In this case, the bacteria have to pass on to their daughter cells two types of cellular polarities simultaneously, their magnetic polarity and the polarity of their motility apparatus. We show here that magnetotactic bacteria of the
Gammaproteobacteria
class pragmatically solve this problem by synthesizing the new flagellum at the division site, a division scheme never observed so far in bacteria. Even though the molecular mechanisms behind this scheme cannot be resolved at the moment due to the lack of genetic tools, this discovery provides a new window into the organizational complexity of simple organisms.