The Epstein-Barr Virus BART miRNA Cluster of the M81 Strain Modulates Multiple Functions in Primary B Cells.

The Epstein-Barr virus (EBV) is a B lymphotropic virus that infects the majority of the human population. All EBV strains transform B lymphocytes, but some strains, such as M81, also induce spontaneous virus replication. EBV encodes 22 microRNAs (miRNAs) that form a cluster within the BART region of the virus and have been previously been found to stimulate tumor cell growth.

The members of an Epstein-Barr virus microRNA cluster cooperate to transform B lymphocytes.

Epstein-Barr virus (EBV) transforms B lymphocytes through the expression of the latent viral proteins EBNA and latent membrane protein (LMP). Recently, it has become apparent that microRNAs (miRNAs) also contribute to EBV's oncogenic properties; recombinant EBVs that lack the BHRF1 miRNA cluster display a reduced ability to transform B lymphocytes in vitro. Furthermore, infected cells evince a marked upregulation of the EBNA genes.

A viral microRNA cluster strongly potentiates the transforming properties of a human herpesvirus.

Epstein-Barr virus (EBV), an oncogenic human herpesvirus, induces cell proliferation after infection of resting B lymphocytes, its reservoir in vivo. The viral latent proteins are necessary for permanent B cell growth, but it is unknown whether they are sufficient. EBV was recently found to encode microRNAs (miRNAs) that are expressed in infected B cells and in some EBV-associated lymphomas.

The Epstein-Barr virus protein kinase BGLF4 and the exonuclease BGLF5 have opposite effects on the regulation of viral protein production.

The Epstein-Barr virus BGLF4 and BGLF5 genes encode a protein kinase and an alkaline exonuclease, respectively. Both proteins were previously found to regulate multiple steps of virus replication, including lytic DNA replication and primary egress. However, while inactivation of BGLF4 led to the downregulation of several viral proteins, the absence of BGLF5 had the opposite effect.

The Epstein-Barr virus alkaline exonuclease BGLF5 serves pleiotropic functions in virus replication.

The Epstein-Barr virus (EBV) alkaline exonuclease BGLF5 has previously been recognized to contribute to immune evasion by downregulating production of HLA molecules during virus replication. We have constructed a BGLF5-null virus mutant to determine BGLF5's functions during EBV viral replication. Quantification of virus production in permissive 293 cells carrying a DeltaBGLF5 genome identified a 17- to 21-fold reduction relative to complemented or wild-type controls.

Epstein-Barr virus B95.8 produced in 293 cells shows marked tropism for differentiated primary epithelial cells and reveals interindividual variation in susceptibility to viral infection.

Epstein-Barr virus (EBV), a well-characterised B-lymphotropic agent is aetiologically linked to B cell lymphoproliferations, but the spectrum of diseases the virus causes also includes oral hairy leukoplakia, a benign epithelial lesion, as well as carcinomas of the nasopharynx and of the stomach. However, it is still unclear how EBV accesses and transforms primary epithelial cells. Sixteen samples consisting of primary epithelial cells from the sphenoidal sinus or from tonsils were infected with GFP-tagged recombinant B95.

Epstein-Barr virus BNRF1 protein allows efficient transfer from the endosomal compartment to the nucleus of primary B lymphocytes.

Epstein-Barr virus (EBV) is a tumor virus with marked B lymphotropism. After crossing the B-cell membrane, the virus enters cytoplasmic vesicles, where decapsidation takes place to allow transfer of the viral DNA to the cell nucleus. BNRF1 has been characterized as the EBV major tegument protein, but its precise function is unknown.

Coactivators p300 and PCAF physically and functionally interact with the foamy viral trans-activator.

Background: Foamy virus Bel1/Tas trans-activators act as key regulators of gene expression and directly bind to Bel1 response elements (BRE) in both the internal and the 5'LTR promoters leading to strong transcriptional trans-activation. Cellular coactivators interacting with Bel1/Tas are unknown to date.

Results: Transient expression assays, co-immunoprecipitation experiments, pull-down assays, and Western blot analysis were used to demonstrate that the coactivator p300 and histone acetyltransferase PCAF specifically interact with the retroviral trans-activator Bel1/Tas in vivo.

Bel1-mediated transactivation of the spumaretroviral internal promoter is repressed by nuclear factor I.

Gene expression of the internal and long terminal repeat promoters of the spuma retrovirus is specifically activated by the transactivator Bel1, the key regulator of viral gene expression. Bel1 directly binds to and activates DNA target sites of viral promoters and those of distinct cellular genes. To determine the contribution of cellular transcription factors to viral transactivation, the viral internal promoter (IP) was analyzed by transient expression, electrophoretic mobility shift assays), and supershifts.

Human spumavirus antibodies in sera from African patients.

Serum samples collected from patients with a wide variety of diseases from African and other countries were tested for antibodies to the human spumaretrovirus (HSRV). A spumaviral env-specific ELISA was employed as screening test. Out of 3020 human sera screened, 106 were found to be positive (3.

Characterization of the transcriptional trans activator of human foamy retrovirus.

The human foamy viruses, or spumaviruses, a distinct subfamily of complex human retroviruses, remain poorly understood both in terms of their pathogenic potential and in terms of the regulatory mechanisms that govern their replication. Here, we demonstrate that the human spumaretrovirus shares with other complex human retroviruses the property of encoding a transcriptional trans activator of the homologous viral long terminal repeat. This regulatory protein is encoded by the viral Bel-1 open reading frame and is localized to the nucleus of expressing cells.

Specific enzyme-linked immunosorbent assay for the detection of antibodies to the human spumavirus.

Recombinant plasmid clones were constructed harbouring the central domains of the outer membrane protein and the transmembrane protein of the env gene of human spumaretrovirus (HSRV). The corresponding fusion proteins were expressed in E. coli, purified and used subsequently to produce antibodies against the HSRV env proteins in rabbits.

Analysis of the primary structure of the long terminal repeat and the gag and pol genes of the human spumaretrovirus.

The nucleotide sequence of the human spumaretrovirus (HSRV) genome was determined. The 5' long terminal repeat region was analyzed by strong stop cDNA synthesis and S1 nuclease mapping. The length of the RU5 region was determined and found to be 346 nucleotides long.

Nucleotide sequence analysis of a cloned DNA fragment from human cells reveals homology to retrotransposons.

During molecular cloning of proviral DNA of human spumaretrovirus, various recombinant clones were established and analyzed. Blot hybridization revealed that one of the recombinant plasmids had the characteristic features of a member of the long interspersed repetitive sequences family. The DNA element was analyzed by restriction mapping and nucleotide sequencing.

The nucleotide sequence of the early region of the Tupaia adenovirus DNA corresponding to the oncogenic region E1b of human adenovirus 7.

The nucleotide sequence of the early region E1b of the tree shrew (Tupaia) adenovirus (TAV) DNA has been determined. The sequenced region includes the genes for polypeptides of Mr 15 000, 44 000 and 13 400, which are analogous to the small and large E1b proteins and protein IX, respectively, of the three human adenovirus serotypes 5, 7, and 12. The hexanucleotide consensus signal AATAAA occurs only at the 3' terminus of the gene for protein IX suggesting that the E1 region of TAV encompasses one transcription unit.