Contents - College of Medical and Dental Sciences - University of ...
Contents - College of Medical and Dental Sciences - University of ...
Contents - College of Medical and Dental Sciences - University of ...
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The 11 th International Workshop on KSHV & Related Agents, Birmingham, UK<br />
Lytic Replication Abstract 41<br />
KSHV ORF57 ENHANCES TRANSLATION OF VIRAL INTRONLESS MRNAS<br />
James R. Boyne, Adam Taylor <strong>and</strong> Adrian Whitehouse<br />
Institute <strong>of</strong> Molecular <strong>and</strong> Cellular Biology, <strong>University</strong> <strong>of</strong> Leeds, Leeds, LS2 9JT, United<br />
Kingdom<br />
Abstract<br />
The majority <strong>of</strong> Kaposi’s sarcoma associated herpesvirus (KSHV) mRNAs lack introns <strong>and</strong><br />
are exported by the ORF57 protein. We have shown that ORF57 binds specifically to<br />
intronless viral mRNAs <strong>and</strong> functions to recruit the human TREX (hTREX) complex, in<br />
contrast to the exon-junction complex, allowing efficient nuclear export <strong>of</strong> the viral<br />
intronless mRNAs. The failure <strong>of</strong> ORF57 to recruit EJC components to viral intronless<br />
mRNAs presents KSHV with an intriguing problem, as the EJC enhances translation <strong>of</strong><br />
cellular spliced mRNAs. The EJC specifically recruits the translation machinery onto the<br />
mRNA via an interaction with the cellular protein PYM, thereby enhancing mRNA<br />
translation. Herein, we demonstrate that KSHV ORF57 functions in translation<br />
enhancement, bypassing the EJC, by recruiting essential cellular translation factors. We<br />
shown, using an in vitro translation assay, that recombinant KSHV ORF57 can enhance<br />
translation <strong>of</strong> an in vitro transcribed KSHV intronless RNA. Moreover, coimmunoprecipitation<br />
assays demonstrate that KSHV ORF57 interacts with PYM <strong>and</strong> 48S<br />
preinitiation components in an RNA-independent manner in both transfected <strong>and</strong><br />
reactivated BCBL cells. Furthermore, GST-pulldown analysis shows that ORF57 only<br />
associates directly with PYM <strong>and</strong> no other members <strong>of</strong> the 48S preinitiation complex. This<br />
suggests that KSHV ORF57 enhances translation by recruiting the 48S preinitiation<br />
complex onto a viral intronless mRNA lacking an EJC, via its direct interaction with PYM.<br />
This data highlights a new role for the ORF57 protein in the KSHV lytic replication cycle.<br />
Presenting author Email: A.Whitehouse@leeds.ac.uk<br />
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