Contents - College of Medical and Dental Sciences - University of ...

The 11 th International Workshop on KSHV & Related Agents, Birmingham, UK
Gene Expression II Abstract 34
ROLE OF MURINE GAMMAHERPESVIRUS-68 ORF37 IN MEDIATING INHIBITION
OF HOST GENE EXPRESSION
L. Roaden 1 , V. Sheridan 1 , B. Lane 1 , R. Sun 2 , B. Dutia 3 and B. Ebrahimi 1
1 Division of Medical Microbiology, School of Infection & Host Defence, University of
Liverpool, Liverpool L69 3GA, UK, 2 Molecular Biology Institute, University of California,
Los Angeles, California, USA, and 3 Centre for Infectious Diseases, Division of Veterinary
Biomedical Sciences, University of Edinburgh, UK.
Abstract
In lytic infection, Murine gammaherpesvirus-68 (MHV-68) and Kaposi’s sarcoma
associated herpesvirus (KSHV) and Epstein-Barr virus have been shown to mediate a
global inhibition of host gene expression. g-herpesviruses, unlike a-herpesviruses, do
not encode RNases. Recently, however, the KSHV ORF37 (an alkaline DNA exonuclease,
also known as SOX) was shown to promote this shutdown by enhancing the degradation
of cellular mRNAs. Similar observations have been made with the EBV homologue of
SOX. Interestingly, SOX does not appear to possess any apparent RNase activity. The
murine gammaherpesvirus-68 (MHV-68) encodes an ORF37 highly homologous to KSHV
ORF37 both at DNA (55% identity) and protein (44% identity) levels. Here we show that
MHV-68 is capable of orchestrating a global repression of cellular gene expression. Using
transient transfection assays and engineered reporters with very rapid half-lives, we
show that ORF37 can independently cause rapid loss of these transcripts when expressed
in transient transfection assays. Using point mutations, we have been able to dissect key
amino acids which may relate to the RNase activity of MHV-68 ORF37. Furthermore, we
have generated a stop mutant of MHV-68 ORF37 to assess the potential shutdown
properties of this viral protein during lytic infection in vitro and in vivo and its potential
role in host gene shut-off during latency and reactivation from latency in vivo.
Presenting author Email: ebrahimi@liv.ac.uk
58