The putative GTPases Nog1p and Lsg1p are required for 60S ribosomal subunit biogenesis and are localized to the nucleus and cytoplasm, respectively.
We characterized two essential putative GTPases, Nog1p and Lsg1p, that are found associated with free 60S ribosomal subunits affinity purified with the nuclear export adapter Nmd3p. Nog1p and Lsg1p are nucleolar and cytoplasmic, respectively, and are not simultaneously on the same particle, reflecting the path of Nmd3p shuttling in and out of the nucleus. Conditional mutants of both NOG1 and LSG1 are defective in 60S subunit biogenesis and display diminished levels of 60S subunits at restrictive temperature. Mutants of both genes also accumulate the 60S ribosomal reporter Rpl25-eGFP in the nucleolus, suggesting that both proteins are needed for subunit export from the nucleolus. Since Lsg1p is cytoplasmic, its role in nuclear export is likely to be indirect. We suggest that Lsg1p is needed to recycle an export factor(s) that shuttles from the nucleus associated with the nascent 60S subunit.
Kallstrom
George
G
Section of Molecular Genetics and Microbiology and Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
Hedges
John
J
Johnson
Arlen
A
D015152:Blotting, Northern; D002352:Carrier Proteins / Q000737:chemistry / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D019084:Fluorescent Antibody Technique, Indirect; D005656:Fungal Proteins / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D017930:Genes, Reporter; D005838:Genotype; D049452:Green Fluorescent Proteins; D028884:Karyopherins / Q000378:metabolism; D007700:Kinetics; D008164:Luminescent Proteins / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000502:physiology*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012335:RNA, Ribosomal / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013696:Temperature; D013997:Time Factors; D000097606:Exportin 1 Protein
D002352:Carrier Proteins; D003513:Cycloheximide; D005656:Fungal Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D049452:Green Fluorescent Proteins; D028884:Karyopherins; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D011500:Protein Synthesis Inhibitors; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D000097606:Exportin 1 Protein; C117894:NMD3 protein, S cerevisiae; C475027:NOG1 protein, S cerevisiae; C475026:LSG1 protein, S cerevisiae