The respiratory syncytial virus matrix protein possesses a Crm1-mediated nuclear export mechanism.
The respiratory syncytial virus (RSV) matrix (M) protein is localized in the nucleus of infected cells early in infection but is mostly cytoplasmic late in infection. We have previously shown that M localizes in the nucleus through the action of the importin beta1 nuclear import receptor. Here, we establish for the first time that M's ability to shuttle to the cytoplasm is due to the action of the nuclear export receptor Crm1, as shown in infected cells, and in cells transfected to express green fluorescent protein (GFP)-M fusion proteins. Specific inhibition of Crm1-mediated nuclear export by leptomycin B increased M nuclear accumulation. Analysis of truncated and point-mutated M derivatives indicated that Crm1-dependent nuclear export of M is attributable to a nuclear export signal (NES) within residues 194 to 206. Importantly, inhibition of M nuclear export resulted in reduced virus production, and a recombinant RSV carrying a mutated NES could not be rescued by reverse genetics. That this is likely to be due to the inability of a nuclear export deficient M to localize to regions of virus assembly is indicated by the fact that a nuclear-export-deficient GFP-M fails to localize to regions of virus assembly when expressed in cells infected with wild-type RSV. Together, our data suggest that Crm1-dependent nuclear export of M is central to RSV infection, representing the first report of such a mechanism for a paramyxovirus M protein and with important implications for related paramyxoviruses.
Ghildyal
Reena
R
Department of Biochemistry and Molecular Biology, Monash University, Melbourne, Victoria, Australia.
Ho
Adeline
A
Dias
Manisha
M
Soegiyono
Lydia
L
Bardin
Phillip G
PG
Tran
Kim C
KC
Teng
Michael N
MN
Jans
David A
DA
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D028884:Karyopherins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D012136:Respiratory Syncytial Viruses / Q000235:genetics / Q000378:metabolism*; D014709:Vero Cells; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication; D000097606:Exportin 1 Protein
D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D014763:Viral Matrix Proteins; D000097606:Exportin 1 Protein