Structure and nuclear import function of the C-terminal domain of influenza virus polymerase PB2 subunit.
The trimeric influenza virus polymerase, comprising subunits PA, PB1 and PB2, is responsible for transcription and replication of the segmented viral RNA genome. Using a novel library-based screening technique called expression of soluble proteins by random incremental truncation (ESPRIT), we identified an independently folded C-terminal domain from PB2 and determined its solution structure by NMR. Using green fluorescent protein fusions, we show that both the domain and the full-length PB2 subunit are efficiently imported into the nucleus dependent on a previously overlooked bipartite nuclear localization sequence (NLS). The crystal structure of the domain complexed with human importin alpha5 shows how the last 20 residues unfold to permit binding to the import factor. The domain contains three surface residues implicated in adaptation from avian to mammalian hosts. One of these tethers the NLS-containing peptide to the core of the domain in the unbound state.
Tarendeau
Franck
F
European Molecular Biology Laboratory (EMBL) Grenoble Outstation, 6 rue Jules Horowitz, BP181, 38042 Grenoble Cedex 9, France.
Boudet
Julien
J
Guilligay
Delphine
D
Mas
Philippe J
PJ
Bougault
Catherine M
CM
Boulo
Sébastien
S
Baudin
Florence
F
Ruigrok
Rob W H
RW
Daigle
Nathalie
N
Ellenberg
Jan
J
Cusack
Stephen
S
Simorre
Jean-Pierre
JP
Hart
Darren J
DJ
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D002470:Cell Survival; D018360:Crystallography, X-Ray; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D009975:Orthomyxoviridae / Q000201:enzymology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism*; D012995:Solubility; D012996:Solutions; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism*; D028901:alpha Karyopherins / Q000737:chemistry
C423142:KPNA1 protein, human; D019913:Nuclear Localization Signals; C502893:PB2 protein, influenza virus; D021122:Protein Subunits; D012996:Solutions; D014764:Viral Proteins; D028901:alpha Karyopherins