Gene regulation by Epstein-Barr virus EBNA2 type 1 and type 2
Author(s)
Lucchesi, Walter
Type
Thesis
Abstract
Epstein-Barr virus, EBV, is a human herpes virus that establishes a life long,
persistent, latent infection in B lymphocytes. In vitro, EBV readily transforms and
immortalizes primary B cells. EBV exists in two types, named EBV type 1 and type
2. These are defined on the basis of polymorphism in the EBNA2 locus. The EBNA2
gene encodes a viral transcription factor that controls viral and cell genes and is
absolutely required for B cell transformation. EBV type 1 strains are much more
efficient than EBV type 2 at transforming B cells and the enhanced transformation
efficiency was previously mapped to the EBNA2 gene.
A transfection assay was devised to compare the ability of type 1 and type 2
EBNA2 to sustain cell proliferation in EREB2.5 lymphoblastoid cells, which contain
a ΔEBNA2-Epstein-Barr virus and express a conditional EBNA2. The reduced
proliferation in cells expressing type 2 EBNA2 correlated with loss of expression of
some cell genes that are known to be targets of type 1 EBNA2. Microarray analysis of
EBNA2 target genes in stably transfected Burkitt lymphoma cells identified a small
number of genes that are more strongly induced by type 1 than type 2 EBNA2 and
one of these genes (CXCR7) was shown to be required for proliferation of
lymphoblastoid cell lines.
The Epstein-Barr virus LMP1 gene is directly induced by EBNA2 and is
critically involved in B cell transformation. In Daudi Burkitt lymphoma cells, EBNA2
type 1 induced LMP1 much more strongly than EBNA2 type 2, although both reached
comparable levels after 48 hours. The results show that differential gene regulation by
Epstein-Barr virus type 1 and type 2 EBNA2 is likely to be the basis for the much
weaker B cell transformation activity of type 2 Epstein-Barr virus strains compared to
type 1 strains.
persistent, latent infection in B lymphocytes. In vitro, EBV readily transforms and
immortalizes primary B cells. EBV exists in two types, named EBV type 1 and type
2. These are defined on the basis of polymorphism in the EBNA2 locus. The EBNA2
gene encodes a viral transcription factor that controls viral and cell genes and is
absolutely required for B cell transformation. EBV type 1 strains are much more
efficient than EBV type 2 at transforming B cells and the enhanced transformation
efficiency was previously mapped to the EBNA2 gene.
A transfection assay was devised to compare the ability of type 1 and type 2
EBNA2 to sustain cell proliferation in EREB2.5 lymphoblastoid cells, which contain
a ΔEBNA2-Epstein-Barr virus and express a conditional EBNA2. The reduced
proliferation in cells expressing type 2 EBNA2 correlated with loss of expression of
some cell genes that are known to be targets of type 1 EBNA2. Microarray analysis of
EBNA2 target genes in stably transfected Burkitt lymphoma cells identified a small
number of genes that are more strongly induced by type 1 than type 2 EBNA2 and
one of these genes (CXCR7) was shown to be required for proliferation of
lymphoblastoid cell lines.
The Epstein-Barr virus LMP1 gene is directly induced by EBNA2 and is
critically involved in B cell transformation. In Daudi Burkitt lymphoma cells, EBNA2
type 1 induced LMP1 much more strongly than EBNA2 type 2, although both reached
comparable levels after 48 hours. The results show that differential gene regulation by
Epstein-Barr virus type 1 and type 2 EBNA2 is likely to be the basis for the much
weaker B cell transformation activity of type 2 Epstein-Barr virus strains compared to
type 1 strains.
Date Issued
2008-12
Date Awarded
2009-06
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Farrell, Paul
Creator
Lucchesi, Walter
Publisher Department
Virology
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)