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The 11 th International Workshop on KSHV & Related Agents, Birmingham, UK
Lytic Replication Abstract 39
RECRUITMENT OF THE COMPLETE HTREX COMPLEX IS REQUIRED FOR KSHV
INTRONLESS MRNA NUCLEAR EXPORT AND VIRUS REPLICATION
James R. Boyne and Adrian Whitehouse
Institute of Molecular and Cellular Biology, University of Leeds, Leeds, LS2 9JT, United
Kingdom
Abstract
The majority of pre-mRNAs in higher eukaryotes contain introns and are exported via
recruitment of the conserved export machinery, TREX, which occurs in a splicingdependent
manner. In contrast, most Kaposi’s sarcoma associated herpesvirus (KSHV)
mRNAs lack introns and are exported by the KSHV ORF57 protein. Herein, we show that
ORF57 functions to recruit the human TREX (hTREX) complex to intronless viral mRNAs
and that this recruitment, but not recruitment of the exon-junction complex, is essential
for nuclear export. The formation of the ORF57-hTREX complex is mediated by a direct
interaction between ORF57 and the export adapter, Aly. We show that a point mutation
in ORF57 which disrupts the ORF57-Aly interaction leads to a failure in both the ORF57mediated
recruitment of hTREX to viral mRNA and their subsequent nuclear export.
Furthermore, using a KSHV replication system we demonstrate that expression of a
trans-dominant Aly mutant disrupts hTREX assembly but retains an ORF57-Aly-TAP
complex on the viral mRNA. Strikingly, in the absence of UAP56 and hTHO-complex we
observed a dramatic decrease in intronless viral mRNA export and virus replication.
These data provide the first direct evidence that the entire hTREX complex is essential for
the export of viral intronless mRNAs and in turn, KSHV replication.
Presenting author Email: bmbjb@bmb.leeds.ac.uk
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