Expression of two related viral early genes in Epstein-Barr virus-associated tumors.
The transcription of two early "leftwardly" expressed genes carrying repetitive sequences, IR2 and IR4, has been studied for Epstein-Barr virus-associated tumors, and for established B-cell lines, using sequence-specific probes generated for this purpose. Whereas the IR4 transcript was identified in every tumor and cell line assessed (except B95-8, with a deletion that removes the gene), expression of the IR2 gene was restricted to B lymphocytes. Though the promoters for both transcripts lie within homologous regions (D(L) and D(R)) in the viral genome, the IR2 promoter appears more tightly regulated. Detailed characterization of the IR4 transcript from a nasopharyngeal carcinoma tumor, C15, identifies a sequence variant of this gene that differs from those reported for B cells; in situ hybridization methods show transcription to be restricted to a subset of cells, with the strongest signals seen adjacent to host stroma. As with B cells in culture (Y. Gao, P. R. Smith, L. Karran, Q. L. Lu, and B. E. Griffin, J. Virol. 71:84-94, 1997), chemical induction enhanced transcriptional expression of the IR4 gene in the C15 tumor, although staining for both the IR4 antigen and that of the virus lytic switch, Zta, gave negative results. In a Burkitt's lymphoma biopsy specimen, however, both proteins were found expressed, notably in the same subset of cells. The data here and elsewhere (Gao et al., J. Virol., 1997) are consistent with a block to intracellular transport of the transcript(s) and suggest nuclear roles for it in tumors, possibly in RNA processing and viral lytic replication. Both roles could be fulfilled in the absence of translation.
Xue
S A
SA
Department of Infectious Diseases (Virology), Imperial College School of Medicine, London W12 ONN, United Kingdom.
Lu
Q L
QL
Poulsom
R
R
Karran
L
L
Jones
M D
MD
Griffin
B E
BE
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002051:Burkitt Lymphoma / Q000473:pathology / Q000821:virology*; D002144:Callithrix; D002460:Cell Line; D003001:Cloning, Molecular; D015342:DNA Probes; D018076:DNA, Complementary; D004279:DNA, Viral; D015967:Gene Expression Regulation, Viral; D017781:Genes, Immediate-Early; D004854:Herpesvirus 4, Human / Q000235:genetics*; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics* / Q000502:physiology; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009303:Nasopharyngeal Neoplasms / Q000473:pathology / Q000821:virology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014764:Viral Proteins / Q000235:genetics* / Q000502:physiology; D054334:Viral Regulatory and Accessory Proteins
D015342:DNA Probes; D018076:DNA, Complementary; D004279:DNA, Viral; C057294:ICP22 protein, human herpesvirus 1; D017874:Immediate-Early Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C078424:EUS1 protein, Equine herpesvirus 1