Functional differences between type 1 and type 2 Epstein-Barr virus EBNA-2
Author(s)
Cancian, Laila
Type
Thesis
Abstract
Epstein-Barr virus (EBV) establishes a lifelong latent infection in the human host. In vitro EBV
immortalises primary B lymphocytes giving rise to latently infected lymphoblastoid cell lines
(LCLs). EBV strains are classified as type 1 or type 2 according to the sequence of the EBNA-2
gene, which expresses a transcription factor that induces viral and cell genes important for B cell
proliferation. Type 1 EBV transforms primary B lymphocytes into LCLs much more efficiently
than type 2 EBV, a difference previously mapped to the EBNA-2 locus.
In this study, the greater transforming activity of type 1 EBV was found to correlate with a
stronger and more rapid induction of the viral oncogene LMP-1 and the cell gene CXCR7 (which
are both required for proliferation of EBV-LCLs) during infection of primary B cells with EBVBAC
recombinant viruses. The enhanced ability of type 1 EBNA-2 to induce LMP-1 and
CXCR7 genes was also confirmed in Burkitt’s Lymphoma cell lines.
Although the major sequence differences between type 1 and type 2 EBNA-2 lie in N-terminal
parts of the protein, the superior ability of type 1 EBNA-2 to sustain proliferation of EBV-LCLs
is mostly determined by the C-terminal region of the protein. Substitution of the C-terminal third
of type 1 EBNA-2 into the type 2 protein is sufficient to confer type 1 growth phenotype and
type 1 expression levels of LMP-1 and CXCR7 in an EREB2.5 cell growth assay. Within this
region, the RG, CR7 and TAD domains are the minimum type 1 sequences required. Sequencing
the C-terminal part of EBNA-2 from additional EBV isolates showed high sequence identity
within type 1 isolates or within type 2 isolates, indicating that the functional differences mapped
are typical of EBV type sequences.
immortalises primary B lymphocytes giving rise to latently infected lymphoblastoid cell lines
(LCLs). EBV strains are classified as type 1 or type 2 according to the sequence of the EBNA-2
gene, which expresses a transcription factor that induces viral and cell genes important for B cell
proliferation. Type 1 EBV transforms primary B lymphocytes into LCLs much more efficiently
than type 2 EBV, a difference previously mapped to the EBNA-2 locus.
In this study, the greater transforming activity of type 1 EBV was found to correlate with a
stronger and more rapid induction of the viral oncogene LMP-1 and the cell gene CXCR7 (which
are both required for proliferation of EBV-LCLs) during infection of primary B cells with EBVBAC
recombinant viruses. The enhanced ability of type 1 EBNA-2 to induce LMP-1 and
CXCR7 genes was also confirmed in Burkitt’s Lymphoma cell lines.
Although the major sequence differences between type 1 and type 2 EBNA-2 lie in N-terminal
parts of the protein, the superior ability of type 1 EBNA-2 to sustain proliferation of EBV-LCLs
is mostly determined by the C-terminal region of the protein. Substitution of the C-terminal third
of type 1 EBNA-2 into the type 2 protein is sufficient to confer type 1 growth phenotype and
type 1 expression levels of LMP-1 and CXCR7 in an EREB2.5 cell growth assay. Within this
region, the RG, CR7 and TAD domains are the minimum type 1 sequences required. Sequencing
the C-terminal part of EBNA-2 from additional EBV isolates showed high sequence identity
within type 1 isolates or within type 2 isolates, indicating that the functional differences mapped
are typical of EBV type sequences.
Date Issued
2011
Date Awarded
2011-10
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Farrell, Paul
Creator
Cancian, Laila
Publisher Department
Medicine
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)