The DEAD-box protein Dbp5p is required to dissociate Mex67p from exported mRNPs at the nuclear rim.
Eukaryotic mRNAs are exported from the nucleus to the cytoplasm as complex mRNA-protein particles (mRNPs), and translocation through the nuclear pore complex (NPC) is accompanied by extensive structural changes of the mRNP. We have tested the hypothesis that the DEAD-box ATPase Dbp5p is required for such an mRNP rearrangement. In dbp5 mutant cells, the mRNA export receptor Mex67p accumulates on mRNA. This aberrant accumulation of Mex67p with RNA and the cold-sensitive growth phenotype of a dbp5 allele are suppressed by a mex67 mutation. Moreover, Mex67 bound mRNA accumulates at the nuclear rim in a temperature-sensitive dbp5 mutant when the nuclear exosome is impaired. Importantly, although accumulation of Mex67p-containing mRNPs is also observed when a nuclear basket component is mutated, these mRNPs still contain the nuclear export factor Yra1p. In contrast, the dbp5-trapped mRNPs lack Yra1p. We propose that Dbp5p's function is specifically required to displace Mex67p from exported mRNPs, thus terminating export.
Lund
Mette K
MK
Department of Biochemistry and Biophysics, Genentech Hall, 600 16th Street, San Francisco, California 94143, USA.
Guthrie
Christine
C
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism*; D053487:DEAD-box RNA Helicases; D009154:Mutation; D009687:Nuclear Proteins / Q000502:physiology*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000502:physiology*; D020365:RNA Helicases / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000502:physiology*; D012261:Ribonucleoproteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*
C106898:MEX67 protein, S cerevisiae; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins; C026452:messenger ribonucleoprotein; C492382:DBP5 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases