An Epstein-Barr virus (EBV)-determined nuclear antigen (EBNA5) partly encoded by the transformation-associated Bam WYH region of EBV DNA: preferential expression in lymphoblastoid cell lines.

114

SUMMARYSeven virus-encoded proteins are regularly expressed in Epstein-Barr virus (EBV)-transformed lymphoblastoid (LCL) cell lines: the EBV nuclear antigens EBNA 1 to 6 and the latent membrane protein (LMP). In nasopharyngeal carcinoma (NPC), only EBNA 1 is regularly expressed; LMP is detected in about 50~ of the tumours. In Burkitt's lymphoma (BL) tumours, only EBNA 1 is expressed. Also, in BL-derived cell lines that maintain the phenotypic markers characteristic of the in vivo tumour (group I), only EBNA 1 is expressed. EBV was rescued by induction or cocultivation from one BL cell line with a restricted group I pattern, and from one NPC tumour, into normal B cells. In the resulting LCLs EBNA 1 to 6 and LMP were expressed. We assessed the level of methylation in the genes encoding EBNA 2 and LMP by restriction fragment analysis using the methylation-sensitive enzymes SmaI and HpalI. These genes were extensively methylated in the group I BL line Rael and the nude mouse-passaged C15 NPC tumour, but were demethylated in the derived LCLs. In the LMP expressing the NPC tumour, but were demethylated in the derived LCLs. In the LMP-expressing coding exons were methylated. The EBNA 1 coding exon was methylated in the Rael line and in NPC, in spite of expression. In contrast, CpG pairs in ori P were originally hypomethylated and remained so after their transfer to LCLs. The cell phenotypedependent pattern of EBV gene methylation correlated with the phenotype-dependent pattern of EBNA and LMP expression. The specific patterns of methylation localized to controlling regions (ori P and 5' flanking sequences) also suggest a specific role for methylation in the regulation of EBNA and LMP expression.

Section: Introductionmentioning

confidence: 99%

The Role of Methylation in the Phenotype-dependent Modulation of Epstein-Barr Nuclear Antigen 2 and Latent Membrane Protein Genes in Cells Latently Infected with Epstein-Barr Virus

Ernberg

Falk

Minárovits

et al. 1989

114

“…At present, the significance of the predicted substitution of carboxy-terminal sequences in Daudi cells is unknown. The demonstration of multiple EBNA5 species in a single EBV-infected B cell line containing a normal B a m H I WYH region is probably due to their expression from mRNAs containing different numbers of W exons (Dillner et al, 1986;Speck et aL, 1986). Since none of the cDNAs characterized in this study represent full-length copies of mRNAs, the exact number of W exons is unknown.…”

mentioning

confidence: 91%

“…The Y2 or Y3 exon is in turn spliced to, or contiguous with, unique 3' sequences which include those encoding EBNAs 1, 2, 3, 4 and 6 (reviewed in Speck & Strominger, 1989). The major part of the remaining member of the EBNA family, EBNA5, is encoded by the W1 and W2 exons, and its carboxy terminus is specified by exons Y1 and Y2 (Dillner et al, 1986;Sample et al, 1986;Speck et al, 1986;Wang et al, 1987 0001-1029 © 1992 SGM present in the 5' leader sequences of messages that specify the other EBNAs. It is noted, however, that such messages can only encode EBNA5 when a translational initiation codon is created by a splicing event at the 5' end of the mRNA (Sample et al, 1986;Speck et al, 1986;Rogers et al, 1990).…”

mentioning

confidence: 99%

Alternative Splicing Determines The Carboxy Terminus of the Epstein--Barr Virus Nuclear Antigen 5 Species Expressed in the Burkitt's Lymphoma Cell Line Daudi

Ring¹,

Jones²,

Griffin³

1992

The Daudi strain of Epstein-Barr virus (EBV) possesses a genomic deletion, relative to the B95-8 EBV prototype, that removes the entire Epstein-Barr virus nuclear antigen 2 (EBNA2) open reading frame (ORF) and the sequences encoding the carboxy terminus of EBNA5. Immunoblot analysis carried out in this study indicates that two species of EBNA5 (31 K and 37K) are expressed in Daudi cells. Nucleotide sequence analysis of Daudi cDNA clones has confirmed that, as a consequence of the genomic deletion, exons usually appearing further downstream in EBNA messages (exons U or HF) are spliced directly onto the truncated EBNA50RF. Furthermore, the use of alternative splicing suggests that the two EBNA5 species expressed in Daudi cells possess different carboxy termini.

“…Several papers have reported characterization of cDNA clones made from mRNAs in lymphocytes latently infected with EBV, and have shown that there exists a class of transcripts which are derived from up to 100000 residues of the EBV genorne Sample et al, 1986). At least some of the five EBV-specified nuclear proteins (EBNAs) associated with maintenance of the genome in its latent state are expressed from this family of mRNAs Dillner et al, 1986). The primary transcripts from which these mRNAs are derived evidently run through many 'normal' genes and transcriptional control signals, and they become multiply spliced, with excision of up to 18 introns, to yield final transcripts of around 2000 residues.…”

mentioning

confidence: 99%

Some Highlights of Animal Virus Research in 1986

McGeoch

Howard

Desselberger

1987

In 1986 we published a review article entitled 'Some highlights of animal virus research in 1985', in which we attempted to summarize important and interesting research on animal viruses published in 1985 (McGeoch et al., 1986b). The limitations of the exercise were recognized: coverage was selective rather than systematic and, outside clearly pre-eminent subjects, was overtly influenced by personal scientific interests. In this article we now present a similar account of animal virology in 1986. Much the same ground rules have been retained. Selectivity remains of the first importance, and our treatment concerns work published in 1986 as far as possible, but with a little flexibility where necessary.As with 1985, animal virology in 1986 was dominated by work on acquired immune deficiency syndrome (AIDS) retroviruses. Outside this area, however, we were not able to identify any small set of truly outstanding advances, although work in many virus systems clearly made excellent progress. This evaluation posed problems for a review of the type undertaken, in particular for achieving a balanced selection of topics. With this background we also found it more necessary than before to address virus groups in separate sections (representing a step back from the previous, integrative stance). We have chosen to present aspects of research on, first, the AIDS viruses, and then in succession on hepatitis viruses, herpesviruses, poxviruses, papovaviruses, picornaviruses and negative strand viruses, and to finish with a section on virion structure. AIDSDuring 1986 the extent of the public health problem posed by AIDS continued to increase worldwide. Certainly, it was in this year that the scale, the immediacy and the longer term implications of this viral disease finally became a prominent part of public consciousness in Great Britain. Prospective cohort studies in Great Britain and in the U.S.A. (Goedert et al., 1986) demonstrated a high and increasing incidence of AIDS 3 to 5 years after infection with the AIDS virus. Also, in 1986, the very wide spread of infection in several Central African countries became much more clearly recognized (Mann et al., 1986a, b;Quinn et al., 1986). Basic research on the retrovirus responsible for AIDS continued to advance rapidly, but problems of treatment and prevention appear to be of a more intransigent nature. On a somewhat bathetic note, we register that the AIDS retrovirus has now been assigned the vernacular name 'human immunodeficiency virus' (HIV) (Coffin et al., 1986;). Here we recount aspects of virus genome structure and variation, gene function, and approaches to countering the virus.The wide variations in the genomes of HIV isolates were further examined. Alizon et al. (1986) determined the complete genomic sequences of two strains from Zaire, in Central Africa. These had biological properties indistinguishable from those of other HIV isolates, and their sequences showed the same layout of reading frames and other features, but sequence comparisons revealed a much greater degr...