Cex1p facilitates Rna1p-mediated dissociation of the Los1p-tRNA-Gsp1p-GTP export complex.
Nuclear tRNA export plays an essential role in key cellular processes such as regulation of protein synthesis, cell cycle progression, response to nutrient availability and DNA damage and development. Like other nuclear export processes, assembly of the nuclear tRNA export complex in the nucleus is dependent on Ran-GTP/Gsp1p-GTP, and dissociation of the export receptor-tRNA-Ran-GTP/Gsp1p-GTP complex in the cytoplasm requires RanBP1/Yrb1p and RanGAP/Rna1p to activate the GTPase activity of Ran-GTP/Gsp1p-GTP. The Saccharomyces cerevisiae Cex1p and Human Scyl1 have also been proposed to participate in unloading of the tRNA export receptors at the cytoplasmic face of the nuclear pore complex (NPC). Here, we provide evidence suggesting that Cex1p is required for activation of the GTPase activity of Gsp1p and dissociation of the receptor-tRNA-Gsp1p export complex in S. cerevisiae. The data suggest that Cex1p recruits Rna1p from the cytoplasm to the NPC and facilitates Rna1p activation of the GTPase activity of Gsp1p by enabling Rna1p to gain access to Gsp1p-GTP bound to the export receptor tRNA complex. It is possible that this tRNA unloading mechanism is conserved in evolutionarily diverse organisms and that other Gsp1p-GTP-dependent export processes use a pathway-specific component to recruit Rna1p to the NPC.
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
Andrew T
AT
McGuire
Dev
D
Mangroo
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D028884:Karyopherins / Q000378:metabolism; D008954:Models, Biological; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism*; D009154:Mutation / Q000502:physiology; D022022:Nuclear Pore / Q000378:metabolism; D028861:Nuclear Pore Complex Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D034443:RNA Transport / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D012353:RNA, Transfer, Gly / Q000378:metabolism; D012365:RNA, Transfer, Tyr / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
C518290:Cex1 protein, S cerevisiae; C080324:GSP1 protein, S cerevisiae; D020690:GTPase-Activating Proteins; D028884:Karyopherins; C408090:Los1 protein, S cerevisiae; C077730:NUP116 protein, S cerevisiae; C400753:NUP2 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D012333:RNA, Messenger; D012353:RNA, Transfer, Gly; D012365:RNA, Transfer, Tyr; D016601:RNA-Binding Proteins; C060997:RNA1 protein, S cerevisiae; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C538902:Srp1 protein, S cerevisiae; C090654:YRB1 protein, S cerevisiae; D006160:Guanosine Triphosphate; D012343:RNA, Transfer; D020558:GTP Phosphohydrolases; D020559:Monomeric GTP-Binding Proteins