EBV Conference 2008 Guangzhou - Baylor College of Medicine

133 (RegID: 1232; 1233)
Thomas Owen
Institution: CRUK Institute for Cancer Studies, University of Birmingham
e-mail: tjo588@bham.ac.uk
IDENTIFICATION OF THE MECHANISM(S) CONTROLLING EBER1/2 RNA EXPRESSION
IN EBV-INFECTED CELLS – A ROLE FOR EBNA1
T.J.Owen, J.D.O’Neil, L.S.Young and J.R.Arrand
Posterabstract:
The EBV-encoded EBER genes are small, untranslated RNAs that are expressed in all forms of EBV
latency and are implicated in EBV-driven oncogenisis. Although the EBERs are subject to regulation by
RNA polymerase III (polIII), relatively little is known about their regulation by other cellular transcription
factors and how EBV can induce high level expression (107 copies) in latently infected cells. The
mechanisms of transcriptional regulation of the EBERs form the focus of our research.
During primary infection of B-lymphocytes, EBER expression occurs after expression of the EBNAs and
LMPs. One hypothesis is another EBV latent gene product may regulate EBER1/2 expression. As
previous findings have uncovered a role for trans-acting factors in controlling transcription of the EBERs,
we sought to identify the EBV-encoded protein responsible for this effect.
Our previous findings have shown that EBV enhances EBER expression through induction of specific
transcription factors. Transcriptional profiling and subsequent validation of EBNA1-expressing cells
revealed that EBNA1 alone was sufficient to induce expression of transcription factors whose activity may
impact on EBER1/2 expression. The generality of these effects was confirmed as EBNA1 was shown to
elevate general polIII transcription in a number of epithelial cell lines. Furthermore, IHC staining revealed
increased expression of TFIIIC subunits and p-ATF2 in NPC tumour biopsies.
To gain an insight into the mechanism by which EBNA1 achieves this effect we performed chromatin
immunoprecipitation (ChIP) analysis on EBNA1 transfected and EBV-infected cells. Using this approach
we demonstrate that EBNA1 is present at promoter elements of ATF2 and c-myc and suggest that this is
the mechanism by which EBNA1 induces their expression. Future work will confirm whether this is also
the case for TFIIIC. The data offer novel insights not only into the transcriptional regulation of the EBERs,
but also the pleiotropic roles of EBNA1 in late
infection.
EBV Conference 2008 Guangzhou
- 197 -