The Marek's disease virus (MDV) protein encoded by the UL17 ortholog is essential for virus growthNajat Chbab1, 2, Danièle Chabanne-Vautherot1, Annick Francineau1, Nikolaus Osterrieder2, Caroline Denesvre1 and Jean-François Vautherot1
1 Laboratoire de Virologie Moléculaire, UR1282 IASP, INRA Centre de Tours, 37380 Nouzilly, France
2 Institute of Virology, Freie Universität Berlin, Philippstrasse 13, 10115 Berlin, Germany
Received 22 April 2008; accepted 12 March 2009; published online 14 March 2009
Abstract - Marek's disease virus type 1 (MDV-1) shows a strict dependency on the direct cell-to-cell spread for its propagation in cell culture. As MDV-1 shows an impaired nuclear egress in cell culture, we wished to address the characterization of capsid/tegument genes which may intervene in the maturation of intranuclear capsids. Orthologs of UL17 are present in all herpesviruses and, in all reported case, were shown to be essential for viral growth, playing a role in capsid maturation and DNA packaging. As only HSV-1 and PrV UL17 proteins have been characterized so far, we wished to examine the role of MDV-1 pUL17 in virus replication. To analyze MDV-1 UL17 gene function, we created deletion mutants or point mutated the open reading frame (ORF) to interrupt its coding phase. We established that a functional ORF UL17 is indispensable for MDV-1 growth. We chose to characterize the virally encoded protein by tagging the 729 amino-acid long protein with a repeat of the HA peptide that was fused to its C-terminus. Protein pUL17 was identified in infected cell extracts as an 82 kDa protein which localized to the nucleus, colocalizing with VP5, the major capsid protein, and VP13/14, a major tegument protein. By using green fluorescent protein fusion and HA tagged proteins expressed under the cytomegalovirus IE gene enhancer/promoter , we showed that MDV-1 pUL17 nuclear distribution in infected cells is not an intrinsic property. Although our results strongly suggest that another viral protein retains (or relocate) pUL17 to the nucleus, we report that none of the tegument protein tested so far were able to mediate pUL17 relocation to the nucleus.
Key words: Marek's disease virus / UL17 / nuclear localization
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© INRA, EDP Sciences 2009