Cytostatic effect of Epstein-Barr virus latent membrane protein-1 analyzed using tetracycline-regulated expression in B cell lines.
Tetracycline-regulated vectors were used to obtain inducible expression in stable transfected B cell lines of two Epstein-Barr virus (EBV) latent genes, LMP1 and EBNA2. The transfected genes were tightly repressed by low, nontoxic concentrations of tetracycline (< or = 1 microgram/ml) and, following removal of tetracycline, were induced to levels comparable to or up to 3x that of EBV-transformed normal lymphoblastoid cell lines. In transfected DG75 cells, induced expression of LMP1, but not of EBNA2, led to the expected upregulation of various cell surface markers, including: CD40, CD54, CD58, and HLA class I.A novel observation was that both LMP1 and EBNA2 independently caused the downregulation of surface IgM, an effect mirrored in EBV-positive Burkitt lymphoma lines undergoing phenotypic drift during the transition from latency I to latency III in which both LMP1 and EBNA2 are upregulated. Most remarkably, induced LMP1 expression almost completely inhibited cell growth for 4 to 5 days, after which the cells recovered a limited proliferative capacity. The cytostatic effect of LMP1 was observed in all three B cell lines studied: DG75, BJAB, and Akata. Further analysis showed that induction of LMP1 coincided with a reduction in the levels of c-myc, and that the cytostatic effect was due to an accumulation of cells at the G2/M phase of the cell cycle. These data suggest a novel function for the LMP1 oncogene in controlling the proliferation of EBV-infected cells by regulating progress through G2/M phase.
Floettmann
J E
JE
Department of Medicine, University of Wales College of Medicine, Heath Park, Cardiff, United Kingdom.
Ward
K
K
Rickinson
A B
AB
Rowe
M
M
D000954:Antigens, Surface / Q000378:metabolism; D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism / Q000821:virology; D002453:Cell Cycle; D002460:Cell Line; D015536:Down-Regulation; D019309:Epstein-Barr Virus Nuclear Antigens / Q000235:genetics / Q000502:physiology; D016195:G2 Phase; D015967:Gene Expression Regulation, Viral; D004854:Herpesvirus 4, Human / Q000502:physiology*; D008938:Mitosis; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D013752:Tetracycline / Q000494:pharmacology; D014162:Transfection; D014763:Viral Matrix Proteins / Q000235:genetics / Q000502:physiology*
D000954:Antigens, Surface; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D019309:Epstein-Barr Virus Nuclear Antigens; D009856:Oncogene Proteins, Viral; D016271:Proto-Oncogene Proteins c-myc; D014763:Viral Matrix Proteins; D013752:Tetracycline