Epstein-Barr virus latent gene expression during the initiation of B cell immortalization.
Epstein-Barr virus (EBV) has the capacity to immortalize a subpopulation of resting B lymphocytes. Lymphoblastoid cell lines (LCL) established in this way carry the latent EBV genome as multiple copies of an extrachromosomal episome. Viral gene expression in LCLs is highly restricted; products identified correspond to a membrane protein (latent membrane protein; LMP), a nuclear antigen complex (Epstein-Barr nuclear antigens; EBNAs 1 to 6), two small RNA species (EBERs 1 and 2) and RNA species thought to encode a second membrane-associated polypeptide designated terminal protein (TP). Here we have investigated the temporal sequence of expression of the characterized 'latent' proteins during the initiation of immortalization when resting B cells are stimulated to enter and traverse the cell cycle. The analysis has been carried out on prolymphocytic leukaemia cells infected in vitro with either the immortalizing B95-8 strain of virus or the non-immortalizing P3HR1 strain. The results reveal that following B95-8 infection, a sequence of EBV expression is initiated within approximately 8 h with the synthesis of detectable levels of EBNA 2 shortly followed by EBNAs 1, 3, 4, 5 and 6. There is then a delay of approximately 40 h until the expression of LMP completes the latent pattern of proteins found in LCLs. P3HR1 infection, however, produces only transient expression of some EBNA species in a small percentage of cells after approximately 48 h. These observations suggest the failure of P3HR1 virus to immortalize may not be due solely to the absence of EBNA 2 expression and that cellular and/or virus-mediated events occur after EBNA synthesis which then facilitate efficient LMP expression and immortalization.
Allday
M J
MJ
Department of Virology, Royal Postgraduate Medical School, London, U.K.
Crawford
D H
DH
Griffin
B E
BE
D000818:Animals; D000956:Antigens, Viral / Q000032:analysis; D001402:B-Lymphocytes / Q000032:analysis / Q000382:microbiology* / Q000473:pathology; D002461:Cell Line, Transformed; D002472:Cell Transformation, Viral; D019309:Epstein-Barr Virus Nuclear Antigens; D005786:Gene Expression Regulation; D005814:Genes, Viral; D004854:Herpesvirus 4, Human / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D006801:Humans; D015463:Leukemia, Prolymphocytic / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology; D051379:Mice; D014763:Viral Matrix Proteins
D000956:Antigens, Viral; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D019309:Epstein-Barr Virus Nuclear Antigens; D014763:Viral Matrix Proteins