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U Zimber-Strobl

Publications and source records attributed to U Zimber-Strobl.

23 records · Page 2Linked to original sources
PubMed1993

The Epstein-Barr virus nuclear antigen 2 interacts with an EBNA2 responsive cis-element of the terminal protein 1 gene promoter.

The Epstein-Barr virus protein EBNA2 acts as a transcriptional activator of cellular and viral genes and plays a crucial role in the immortalization of human primary B-cells by EBV. We have shown previously that EBNA2 transactivates the promoters of the latent membrane antigens LMP, TP1 and TP2. The promoter of the TP1 gene was chosen as a model system to study the molecular mechanism of EBNA2 mediated transactivation. To identify an EBNA2 dependent cis-acting element, various TP1 promoter-reporter gene constructs were transfected in the absence and presence of an EBNA2 expression vector into the established B-cell line BL41-P3HR1. We were able to delineate an 81 bp EBNA2 responsive region between -258 and -177 relative to the TP1 RNA start site. The element worked in either orientation and could mediate EBNA2 dependent transactivation on a heterologous promoter. Electrophoretic mobility shift assays revealed three specific protein-DNA complexes formed with sequences of the EBNA2 responsive element. Two of these were not cell type specific, but the third was detected only in EBNA2 positive cell extracts. Gel-shift analysis in the presence of EBNA2 specific monoclonal antibodies revealed that EBNA2 is a component of the third complex. Thus, these experiments demonstrate that EBNA2 interacts with an EBNA2 responsive cis-element of the TP1 promoter.

Antigens, Surface↗
PubMed1993

Characterization of the antibody response to the latent infection terminal proteins of Epstein-Barr virus in patients with nasopharyngeal carcinoma.

Human sera were tested for antibodies against the Epstein-Barr virus (EBV) latent infection terminal proteins (TPs). Anti-TP IgG and IgA antibodies were detected by an indirect immunofluorescence assay of insect cells expressing a recombinant TP1. Out of 301 human sera of patients with EBV-related and EBV-unrelated disorders, only sera from patients with nasopharyngeal carcinoma (NPC) (32/83; 38%) showed anti-TP antibodies. Studies on serial sera from German and Hong Kong NPC patients revealed a decline of anti-TP antibodies during tumour therapy, and none of these antibodies were identified in patients with early tumour stages or in remission. Comparative studies of TP1-specific polyclonal rabbit antisera and human TP-positive sera showed clear differences in the TP epitopes recognized by each. Human antisera contained antibodies only to native epitopes in exons 2 to 7 of TP1 whereas rabbit antisera reacted only with epitopes located in the first exon and, additionally, exhibited EBV strain specificities.

Animals↗
PubMed1991

Epstein-Barr virus nuclear antigen 2 activates transcription of the terminal protein gene.

Transcription of the terminal protein (TP) gene of Epstein-Barr virus (EBV) in Burkitt's lymphoma cells, in EBV-negative Burkitt's lymphoma cells converted with transformation-defective (P3HR1) and transformation-competent (B95-8, AG876) EBV strains, and in EBV-immortalized cell lines was studied. A TP1 cDNA probe spanning the boundary between exons 1 and 2 and discriminating between TP1 and TP2 transcripts was used for S1 analysis. TP RNA expression varied widely in Burkitt's lymphoma cells. TP-specific transcripts were not detectable or only hardly detectable in Burkitt's lymphoma cells with the group I phenotype (CD10+ CD77+ CD21- CD23- CD30- CDw70-) as well as in P3HR1 virus-converted Burkitt's lymphoma lines. TP expression was high in Burkitt's lymphoma lines with the group II and group III phenotypes (CD21+ CD23+ CD30+ CDw70+), in B95-8 and AG876 virus-converted lines, and in EBV-immortalized cells. Detection of TP1 RNA correlated with EBNA2 expression. TP1 transcription was shown to be dependent on EBNA2 expression by stable transfection of an EBNA2 expression vector into P3HR1 virus-converted BL41 cells. EBNA2 is activating the TP1 as well as the TP2 promoter, as shown by the analysis of TP promoter-chloramphenicol acetyltransferase constructs transiently transfected into EBNA2-positive and EBNA2-negative Burkitt's lymphoma cells.

Antigens, Viral↗
PubMed1990

Identification of Epstein-Barr virus terminal protein 1 (TP1) in extracts of four lymphoid cell lines, expression in insect cells, and detection of antibodies in human sera.

The terminal proteins TP1 and TP2 are putative products of Epstein-Barr virus (EBV) genes expressed during the latent cycle of the virus. They are predicted to code for 53- and 40-kilodalton integral membrane proteins. We used the baculovirus Autographa californica nuclear polyhedrosis virus as an expression vector to produce TP1 in large amounts in insect cells. The DNA sequences used to express TP1 originated from a TP1 cDNA derived from an M-ABA/CBL1 cDNA library. Rabbit antisera raised against procaryotic TP1 fusion proteins recognized a monomer and a dimer of the recombinant TP1 protein in the infected insect cells. Immunofluorescence studies of living insect cells showed that the recombinant protein is located in the plasma membrane. The insect cells infected with the recombinant baculovirus producing TP1 provided a test system to screen human antisera for TP1 antibodies. A total of 168 human EBV-positive and EBV-negative antisera were studied. TP1 antibodies were detected only in sera from nasopharyngeal carcinoma patients (16 out of 42). Rabbit antiserum raised against the recombinant TP1 protein expressed in the baculovirus system specifically recognized a protein of about 54 kilodaltons in the lymphoblastoid cell lines M-ABA and M-ABA/CBL1 and in the Burkitt's lymphoma cell lines BL18 and BL72. This protein could be located in the total membrane fraction of M-ABA cells and is upregulated by treating the cells with 12-O-tetradecanoylphorbol-13-acetate.

Animals↗