A supraphysiological nuclear export signal is required for parvovirus nuclear export.
CRM1 exports proteins that carry a short leucine-rich peptide signal, the nuclear export signal (NES), from the nucleus. Regular NESs must have low affinity for CRM1 to function optimally. We previously generated artificial NESs with higher affinities for CRM1, termed supraphysiological NESs. Here we identify a supraphysiological NES in an endogenous protein, the NS2 protein of parvovirus Minute Virus of Mice (MVM). NS2 interacts with CRM1 without the requirement of RanGTP, whereas addition of RanGTP renders the complex highly stable. Mutation of a single hydrophobic residue that inactivates regular NESs lowers the affinity of the NS2 NES for CRM1 from supraphysiological to regular. Mutant MVM harboring this regular NES is compromised in viral nuclear export and productivity. In virus-infected mouse fibroblasts we observe colocalization of NS2, CRM1 and mature virions, which is dependent on the supraphysiological NS2 NES. We conclude that supraphysiological NESs exist in nature and that the supraphysiological NS2 NES has a critical role in active nuclear export of mature MVM particles before cell lysis.
Engelsma
Dieuwke
D
Department of Tumor Biology, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.
Valle
Noelia
N
Fish
Alexander
A
Salomé
Nathalie
N
Almendral
José M
JM
Fornerod
Maarten
M
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism* / Q000821:virology*; D006801:Humans; D028884:Karyopherins / Q000378:metabolism; D051379:Mice; D008915:Minute Virus of Mice / Q000378:metabolism* / Q000472:pathogenicity; D018832:Molecular Chaperones / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000378:metabolism; D049790:Nuclear Export Signals; D028861:Nuclear Pore Complex Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D017361:Viral Nonstructural Proteins / Q000737:chemistry / Q000378:metabolism*; D014771:Virion / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000378:metabolism; D000097606:Exportin 1 Protein
D028884:Karyopherins; D018832:Molecular Chaperones; D049790:Nuclear Export Signals; D028861:Nuclear Pore Complex Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D017361:Viral Nonstructural Proteins; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein; C505067:NS2 protein, minute virus of mice; C094493:ran-binding protein 2