Dbp5, a DEAD-box protein required for mRNA export, is recruited to the cytoplasmic fibrils of nuclear pore complex via a conserved interaction with CAN/Nup159p.
Dbp5 is a DEAD-box protein essential for mRNA export from the nucleus in yeast. Here we report the isolation of a cDNA encoding human Dbp5 (hDbp5) which is 46% identical to yDbp5p. Like its yeast homologue, hDbp5 is localized within the cytoplasm and at the nuclear rim. By immunoelectron microscopy, the nuclear envelope-bound fraction of Dbp5 has been localized to the cytoplasmic fibrils of the nuclear pore complex (NPC). Consistent with this localization, we show that both the human and yeast proteins directly interact with an N-terminal region of the nucleoporins CAN/Nup159p. In a conditional yeast strain in which Nup159p is degraded when shifted to the nonpermissive temperature, yDbp5p dissociates from the NPC and localizes to the cytoplasm. Thus, Dbp5 is recruited to the NPC via a conserved interaction with CAN/Nup159p. To investigate its function, we generated defective hDbp5 mutants and analysed their effects in RNA export by microinjection in Xenopus oocytes. A mutant protein containing a Glu-->Gln change in the conserved DEAD-box inhibited the nuclear exit of mRNAs. Together, our data indicate that Dbp5 is a conserved RNA-dependent ATPase which is recruited to the cytoplasmic fibrils of the NPC where it participates in the export of mRNAs out of the nucleus.
Schmitt
C
C
University of Geneva, Department of Molecular Biology, 30 quai Ernest-Ansermet, CH-1205 Geneva.
von Kobbe
C
C
Bachi
A
A
Panté
N
N
Rodrigues
J P
JP
Boscheron
C
C
Rigaut
G
G
Wilm
M
M
Séraphin
B
B
Carmo-Fonseca
M
M
Izaurralde
E
E
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D001692:Biological Transport; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003593:Cytoplasm / Q000378:metabolism*; D053487:DEAD-box RNA Helicases; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009685:Nuclear Envelope / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D020365:RNA Helicases; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
D005656:Fungal Proteins; D008565:Membrane Proteins; C093510:NUP159 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D000251:Adenosine Triphosphatases; C121148:DDX19B protein, human; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases