Varicella-zoster virus IE4 protein interacts with SR proteins and exports mRNAs through the TAP/NXF1 pathway.
Available data suggest that the Varicella-Zoster virus (VZV) IE4 protein acts as an important regulator on VZV and cellular genes expression and could exert its functions at post-transcriptional level. However, the molecular mechanisms supported by this protein are not yet fully characterized. In the present study, we have attempted to clarify this IE4-mediated gene regulation and identify some cellular partners of IE4. By yeast two-hybrid and immunoprecipitation analysis, we showed that IE4 interacts with three shuttling SR proteins, namely ASF/SF2, 9G8 and SRp20. We positioned the binding domain in the IE4 RbRc region and we showed that these interactions are not bridged by RNA. We demonstrated also that IE4 strongly interacts with the main SR protein kinase, SRPK1, and is phosphorylated in in vitro kinase assay on residue Ser-136 contained in the Rb domain. By Northwestern analysis, we showed that IE4 is able to bind RNA through its arginine-rich region and in immunoprecipitation experiments the presence of RNA stabilizes complexes containing IE4 and the cellular export factors TAP/NXF1 and Aly/REF since the interactions are RNase-sensitive. Finally, we determined that IE4 influences the export of reporter mRNAs and clearly showed, by TAP/NXF1 knockdown, that VZV infection requires the TAP/NXF1 export pathway to express some viral transcripts. We thus highlighted a new example of viral mRNA export factor and proposed a model of IE4-mediated viral mRNAs export.
Ote
Isabelle
I
Laboratory of Virology and Immunology, GIGA-R, University of Liege (ULg), Liège, Belgium.
Lebrun
Marielle
M
Vandevenne
Patricia
P
Bontems
Sébastien
S
Medina-Palazon
Cahora
C
Manet
Evelyne
E
Piette
Jacques
J
Sadzot-Delvaux
Catherine
C
D001120:Arginine / Q000737:chemistry; D001692:Biological Transport; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D006367:HeLa Cells; D014645:Herpesvirus 3, Human / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism* / Q000502:physiology*; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors
D017874:Immediate-Early Proteins; C122111:NXF1 protein, human; D029543:Nucleocytoplasmic Transport Proteins; C085824:ORF4 protein, Human herpesvirus 3; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C491388:SRSF3 protein, human; D000068103:Serine-Arginine Splicing Factors; D001120:Arginine; D012260:Ribonucleases