Epstein-Barr Virus BamHI W Repeat Number Limits EBNA2/EBNA-LP Coexpression in Newly Infected B Cells and the Efficiency of B-Cell Transformation: a Rationale for the Multiple W Repeats in Wild-Type Virus Strains
| Autor: | Kuan-Yu Kao, Rosemary J. Tierney, Jasdeep Nagra, Alan B. Rickinson |
|---|---|
| Rok vydání: | 2011 |
| Předmět: |
Epstein-Barr Virus Infections
Herpesvirus 4 Human viruses Immunology Mutant Biology Real-Time Polymerase Chain Reaction medicine.disease_cause Microbiology Genome Virus law.invention Viral Proteins law hemic and lymphatic diseases Virology medicine Humans Gene Cells Cultured Repetitive Sequences Nucleic Acid Genetics B-Lymphocytes Cell Transformation Viral Epstein–Barr virus Virus-Cell Interactions Transformation (genetics) Epstein-Barr Virus Nuclear Antigens Insect Science Recombinant DNA RNA Viral BamHI |
| Zdroj: | Journal of Virology. 85:12362-12375 |
| ISSN: | 1098-5514 0022-538X |
| DOI: | 10.1128/jvi.06059-11 |
| Popis: | The genome of Epstein-Barr virus (EBV), a gammaherpesvirus with potent B-cell growth-transforming ability, contains multiple copies of a 3-kb BamHI W repeat sequence; each repeat carries (i) a promoter (Wp) that initiates transformation by driving EBNA-LP and EBNA2 expression and (ii) the W1W2 exons encoding the functionally active repeat domain of EBNA-LP. The W repeat copy number of a virus therefore influences two potential determinants of its transforming ability: the number of available Wp copies and the maximum size of the encoded EBNA-LP. Here, using recombinant EBVs, we show that optimal B-cell transformation requires a minimum of 5 W repeats (5W); the levels of transforming ability fall progressively with viruses carrying 4, 3, and 2 W repeats, as do the levels of Wp-initiated transcripts expressed early postinfection (p.i.), while viruses with 1 copy of the wild-type W repeat (1W) and 0W are completely nontransforming. We therefore suggest that genetic analyses of EBV transforming function should ensure that wild-type and mutant strains have equal numbers (ideally at least 5) of W copies if the analysis is not to be compromised. Attempts to enhance the transforming function of low-W-copy-number viruses, via the activity of helper EBV strains or by gene repair, suggested that the critical defect is not related to EBNA-LP size but to the failure to achieve sufficiently strong coexpression of EBNA-LP and EBNA2 early postinfection. We further show by the results of ex vivo assays that EBV strains in the blood of infected individuals typically have a mean of 5 to 8 W copies, consistent with the view that evolution has selected for viruses with an optimal transforming function. |
| Databáze: | OpenAIRE |
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