Biomedical subjects

Fritz Schwarzmann

Publications and source records attributed to Fritz Schwarzmann.

7 recordsLinked to original sources

PubMed2004

EBV-associated neoplasms: alternative pathogenetic pathways.

We propose that there are two main classes of Epstein-Barr virus (EBV) associated lymphomas: primarily malignant Burkitt's Lymphoma (BL) and Hodgkin's Disease (HD), on one hand, and primarily benign lymphoproliferations, e.g., post-transplant lymphoproliferative disease (PTLD) on the other hand. PTLD may start as a benign lymphoproliferation which becomes malignant if out of T cell control for too long. Our discovery of a binding site for the oncoprotein c-Myc at a central position of the EBV genome favours a distinction of pathogenetic pathways or scenarios for the proposed lymphoma classes. In the first scenario nuclear maintenance of the EBV genome and activation of viral anti-apoptotic functions with the help of c-Myc are indispensable for the origin of malignant tumours (BL, HD) from the germinal centre B-cell. In the second scenario expression of the main viral transforming protein EBNA2 is essential for immortalisation and non-malignant morphological transformation of any (germinal centre derived or non-germinal centre) B-cell in the absence of T cell control. Although EBNA2 expression is permissible, under specific circumstances, in malignant B-cells, it is not required for oncogenesis.

Burkitt Lymphoma↗

PubMed2004

The LCR of EBV makes Burkitt's lymphoma endemic.

The spectacular ability of Epstein-Barr virus (EBV) to immortalize and morphologically transform human B cells in vitro to lymphoblastoid cell lines (LCLs) is central to most molecular models of viral oncogenesis. However, binding of transcription factor and oncoprotein c-Myc to the major locus control region (LCR) of the viral genome directs us to an alternative model for the origin of Burkitt's lymphoma (BL). In this model, improved nuclear maintenance of the viral genome and the continuous expression of anti-apoptotic functions in B cells exhibiting class I EBV latency contribute to the generation of BL, without any detour through EBV nuclear antigen (EBNA) 2-driven B-cell immortalization (also called class III latency).

Apoptosis↗

PubMed2004

The reading frame BPLF1 of Epstein-Barr virus: a homologue of herpes simplex virus protein VP16.

The open reading frame BPLF1 of Epstein-Barr virus (EBV) shows homology to the Herpes simplex virus 1 (HSV1) protein VP16. This protein is a structural tegument component playing a pivotal role for HSV replication as trans-activator of viral immediate-early genes. An EBV gene with a comparable function has not been described so far. However, computer analysis indicated that BPLF1 may be a tegument protein homologous to VP16. This is the first report on the characterisation of the BPLF1 gene, its transcription, and expression of its gene product in vitro and in vivo. Using RT-PCR and Northern blot assays we demonstrated that the BPLF1 gene belongs to the class of late lytic cycle genes of EBV. Besides a full length transcript of 9.5 kb also a polyadenylated transcript of approximately 3 kb is synthesised. However, no consensus splice sites could be identified. Northern blot experiments using partially overlapping probes and sequencing of a BPLF1-specific cDNA revealed 1,550 nucleotides of the BPLF1 transcript, collinear in sequence with the viral genome from position 64547 to 66097. A recombinant Western blot assay detected BPLF1-specific antibodies in seropositive individuals, in particular in cases with elevated viral replication like infectious mononucleosis, chronic active infection, and nasopharyngeal carcinoma. This demonstrated expression of the BPLF1 protein in vivo. Thus, experimental data and computer analysis strongly support the hypothesis of BPLF1 being a tegument protein of the EBV homologous to VP16 of HSV1 and ORF22 of Varicella zoster virus.

Animals↗

PubMed2003

High-resolution methylation analysis and in vivo protein-DNA binding at the promoter of the viral oncogene LMP2A in B cell lines carrying latent Epstein-Barr virus genomes.

Latency protein LMP2A of Epstein-Barr virus (EBV) has been implicated in EBV related tumorigenesis. To understand the host cell dependent expression of the LMP2A gene, it is necessary to analyse the regulatory mechanisms of the LMP2A promoter (LMP2Ap). By transient transfection and in vitro binding analyses two CBF1 sites have previously been shown to be involved in the regulation of LMP2Ap. However, the promoter structure has not been examined at the nucleotide level in vivo. Therefore we undertook a comprehensive analysis of in vivo protein binding and of CpG-methylation patterns at LMP2Ap in a panel of B cell lines carrying latent EBV genomes. The presence of characteristic footprints on two CBF1 and further binding-sites, together with overall hypomethylation of CpG dinucleotides correlated well with promoter activity. In contrast, the absence of several genomic footprints, as well as the presence of patches of highly methylated CpG dinucleotides were characteristic of silent LMP2Aps.

B-Lymphocytes↗

PubMed2003

The BZLF1 promoter of Epstein-Barr virus is controlled by E box-/HI-motif-binding factors during virus latency.

The BZLF1 open reading frame of Epstein-Barr virus (EBV) encodes an important transactivator of replication. During latency, transcription of this gene is switched off. HI motifs have been shown to cause negative regulation of the promoter. Using yeast one-hybrid assays, we isolated the E box-binding protein, E2-2, interacting with these motifs. Electrophoretic mobility shift assays demonstrated that E2-2 binds to HI alpha, HI beta and HI gamma, which contain E box consensus binding sites. Deletion of the HI-associated E boxes and overexpression of E2-2 in transfection assays revealed that these elements act as repressors in lymphoid cells. In contrast, in epithelial cells they contribute to the increased responsiveness of the promoter to transactivation by the BZLF1 protein. The data presented are in accord with an alternative and exclusive binding of different cell type- and differentiation-specific factors, such as E2-2, to the HI-associated E boxes in lymphoid and epithelial cells. This implies a role in cell type-specific virus replication.

Cell Line↗

PubMed2003

The in vivo binding site for oncoprotein c-Myc in the promoter for Epstein-Barr virus (EBV) encoding RNA (EBER) 1 suggests a specific role for EBV in lymphomagenesis.

BACKGROUND: Epstein-Barr virus (EBV) was isolated in the 1960s from the African childhood tumor, Burkitt's Lymphoma (BL), characterized by the translocation of the c-myc gene into one of the immunoglobulin loci. Due to the extreme discrepancy between the widespread dissemination of EBV infection and the overall rarity of EBV-related tumors, it remains an open question whether EBV is really a human tumor virus, and if so, what specific contribution EBV may have to tumorigenesis. MATERIAL/METHODS: Protein binding at the EBER locus of EBV was analyzed by genomic footprinting electrophoretic mobility shift, reporter gene assay, and chromatin immunoprecipitation in a panel of six B-cell lines. RESULTS: Several novel in vivo protein binding sites were found in the EBER locus. Among those, a prominent binding site, 130 base pairs upstream of the EBER1 gene, contains two E-boxes providing a consensus sequence for binding of the transcription factor and oncoprotein c-Myc to the EBV genome. CONCLUSIONS: Based on the discovery of a binding site for c-Myc in the EBV genome, a new molecular model for the specific role of EBV as a causal factor in the origin of endemic Burkitt's Lymphoma is proposed. Translocated and deregulated c-myc directly activates and maintains the antiapoptotic functions of the EBER locus in a single EBV-infected B cell undergoing the germinal center (GC) reaction. With the balance shifted towards cell survival, the oncogenic potential of the pro-apoptotic c-Myc protein is unmasked in the translocated GC cell. This single translocated and surviving cell is the founder cell of an endemic BL. The new model reinstitutes EBV as a real human tumor virus.

Binding Sites↗

PubMed2002

Nucleoprotein structure of immediate-early promoters Zp and Rp and of oriLyt of latent Epstein-Barr virus genomes.

Genomic footprints across Rp, Zp, and oriLyt of Epstein-Barr virus (EBV) have been conducted in a panel of latently infected B-cell lines. Close protein-base contacts were found about 360 nucleotides upstream of the Zp initiation site. Gel shifts and transient transfection assays indicated that an Sp1-NF1 locus may serve as a repressive transcriptional element against Zp induction from latent EBV genomes.

B-Lymphocytes↗