Search results for "viruses"
showing 10 items of 1182 documents
Recombination profiles between Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus in laboratory and field conditions: evolution…
2012
Tomato yellow leaf curl Sardinia virus and Tomato yellow leaf curl virus have co-existed in Italian tomato crops since 2002 and have reached equilibrium, with plants hosting molecules of both species plus their recombinants being the most frequent case. Recombination events are studied in field samples, as well as in experimental co-infections, when recombinants were detected as early as 45 days following inoculation. In both conditions, recombination breakpoints were essentially absent in regions corresponding to ORFs V2, CP and C4, whereas density was highest in the 3′-terminal portion of ORF C3, next to the region where the two transcription units co-terminate. The vast majority of brea…
Transcriptional activation of apurinic/apyrimidinic endonuclease (Ape, Ref-1) by oxidative stress requires CREB.
1999
Abstract Apurinic/apyrimidinic endonuclease (APE alias Ref-1) is a multifunctional enzyme involved in DNA repair and redox regulation of transcription factors (e.g., AP-1). It also acts as a repressor of its own and other genes. Recently, it was shown that the level of APE mRNA and protein is enhanced upon treatment of cells with oxidative agents, such as hydrogen peroxide (H 2 O 2 ), which gives rise to an adaptive response of cells to oxidative stress. Induction of APE is due to APE promoter activation. To elucidate the mechanism of transcriptional activation of APE by oxidative agents, we introduced mutations into the cloned human APE promoter and checked its activity in transient transf…
NFAT transcription factors control HIV-1 expression through a binding site downstream of TAR region.
2004
NFAT factors control HIV-1 transcription. We show here that, in addition to binding to two NF-kappaB/NFAT sites within the U3 HIV LTR, NFATc1 and NFATc2 bind to an NFAT site within the LTR's U5 region. Mutations in this site which abolish NFAT binding reduce the ability of NFATs to transactivate LTR-mediated transcription. Mutations in all three NFAT sites strongly interfered with LTR induction, but affected moderately the stimulatory effect of Tat.
CD8 T Cells Control Cytomegalovirus Latency by Epitope-Specific Sensing of Transcriptional Reactivation
2006
ABSTRACT During murine cytomegalovirus (mCMV) latency in the lungs, most of the viral genomes are transcriptionally silent at the major immediate-early locus, but rare and stochastic episodes of desilencing lead to the expression of IE1 transcripts. This low-frequency but perpetual expression is accompanied by an activation of lung-resident effector-memory CD8 T cells specific for the antigenic peptide 168-YPHFMPTNL-176, which is derivedfrom the IE1 protein. These molecular and immunological findings were combined in the “silencing/desilencing and immune sensing hypothesis” of cytomegalovirus latency and reactivation. This hypothesis proposes that IE1 gene expression proceeds to cell surfac…
Transactivation of cellular genes involved in nucleotide metabolism by the regulatory IE1 protein of murine cytomegalovirus is not critical for viral…
2008
ABSTRACT Despite its high coding capacity, murine CMV (mCMV) does not encode functional enzymes for nucleotide biosynthesis. It thus depends on cellular enzymes, such as ribonucleotide reductase (RNR) and thymidylate synthase (TS), to be supplied with deoxynucleoside triphosphates (dNTPs) for its DNA replication. Viral transactivation of these cellular genes in quiescent cells of host tissues is therefore a parameter of viral fitness relevant to pathogenicity. Previous work has shown that the IE1, but not the IE3, protein of mCMV transactivates RNR and TS gene promoters and has revealed an in vivo attenuation of the mutant virus mCMV-ΔIE1. It was attractive to propose the hypothesis that la…
Human genetic polymorphisms and risk of viral infection after solid organ transplantation.
2021
The immune system plays a key role in the host defense against viral pathogens. A signaling cascade is activated upon infection involving a variety of molecules such as pattern-recognition receptors (PRRs), interleukins or antiviral interferons. Long-term immunosuppression after solid organ transplantation (SOT) mainly abrogates adaptive T-cell-mediated responses, thus highlighting the relative contribution of innate immunity. Single-nucleotide polymorphisms (SNPs) within genes coding for PRRs or soluble mediators have been associated with differential susceptibility to viral infections among SOT recipients. A protective effect against cytomegalovirus (CMV) infection or disease has been att…
Tirant is a new member of the gypsy family of retrotransposons in Drosophila melanogaster.
2000
In this paper, we propose a consensus sequence for a putative complete Tirant retrotransposon. Several defective copies, as well as relevant sequences available in databases have been analyzed. The putative complete Tirant element is 8533 bp long, and presents all the structural features of a retroviruslike transposable element of the gypsy family. It contains three ORFs (open reading frames) that encode putative products resembling the retroviral Gag, Pol, and Env proteins. Southern blot analyses show that complete and defective Tirant elements are widespread in Drosophila melanogaster. The different hybridization patterns observed in several natural populations of this species suggest tha…
bilbo, a non-LTR retrotransposon of Drosophila subobscura: a clue to the evolution of LINE-like elements in Drosophila
1997
We used the repetitive character of transposable elements to isolate a non-LTR retrotransposon in Drosophila subobscura. bilbo, as we have called it, has homology to TRIM and LOA elements. Sequence analysis showed a 5' untranslated region (UTR), an open reading frame (ORF) with no RNA-binding domains, a downstream ORF that had structural homology to that of the I factor, and, finally, a 3' UTR which ended in several 5-nt repeats. The results of our phylogenetic and structural analyses shed light on the evolution of Drosophila non-LTR retrotransposons and support the hypothesis that an ancestor of these elements was structurally complex.
dsRNA induces apoptosis through an atypical death complex associating TLR3 to caspase-8
2012
Toll-like receptor 3 (TLR3) is a pattern-recognition receptor known to initiate an innate immune response when stimulated by double-stranded RNA (dsRNA). Components of TLR3 signaling, including TIR domain-containing adapter inducing IFN-α (TRIF), have been demonstrated to contribute to dsRNA-induced cell death through caspase-8 and receptor interacting protein (RIP)1 in various human cancer cells. We provide here a detailed analysis of the caspase-8 activating machinery triggered in response to Poly(I:C) dsRNA. Engagement of TLR3 by dsRNA in both type I and type II lung cancer cells induces the formation of an atypical caspase-8-containing complex that is devoid of classical death receptors…
Influence of double infections on the induction of thymidine kinase by UV-irradiated herpes simplex virus types 1 and 2 and pseudorabies virus
1975
Simultaneous infection of primary rabbit kidney cells with HSV type 1 TK+ and a TK- strain results in a mutual influence of both viruses on the induction of thymidine kinase (TK). TK+ virus has an enhancing and TK- virus a depressing effect on TK induction by a superinfecting TK+ virus. The enzyme induction depends on the ratio of multiplicities of both viruses. The mutual influence on TK induction depends further on the time of addition of the superinfecting virus: the effect of the second virus can still be observed when given 6 hours after primary infection. Identical phenomena can be observed using combinations with HSV type 2 or Pseudorabies viruses. The ability of HSV to induce TK is …