Abstract
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.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Blotting, Northern
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Carrier Proteins / chemistry
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Carrier Proteins / physiology*
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Cell Nucleus / metabolism*
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Cycloheximide / pharmacology
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Cytoplasm / metabolism*
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Electrophoresis, Polyacrylamide Gel
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Exportin 1 Protein
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Fluorescent Antibody Technique, Indirect
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Fungal Proteins / metabolism*
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GTP Phosphohydrolases / chemistry
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GTP Phosphohydrolases / physiology*
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GTP-Binding Proteins / chemistry
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GTP-Binding Proteins / physiology*
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Genes, Reporter
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Genotype
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Green Fluorescent Proteins
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Karyopherins / metabolism
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Kinetics
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Luminescent Proteins / metabolism
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Models, Biological
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Mutation
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Nuclear Proteins / chemistry
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Nuclear Proteins / physiology*
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Plasmids / metabolism
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Precipitin Tests
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Protein Binding
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Protein Biosynthesis
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Protein Synthesis Inhibitors / pharmacology
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RNA, Ribosomal / metabolism
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RNA-Binding Proteins / metabolism
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Receptors, Cytoplasmic and Nuclear*
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Recombinant Fusion Proteins / metabolism
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Ribosomes / metabolism*
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Saccharomyces cerevisiae Proteins / metabolism
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Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
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Temperature
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Time Factors
Substances
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Carrier Proteins
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Fungal Proteins
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Karyopherins
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Luminescent Proteins
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NMD3 protein, S cerevisiae
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NOG1 protein, S cerevisiae
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Nuclear Proteins
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Protein Synthesis Inhibitors
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RNA, Ribosomal
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RNA-Binding Proteins
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Receptors, Cytoplasmic and Nuclear
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae Proteins
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Green Fluorescent Proteins
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Cycloheximide
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GTP Phosphohydrolases
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GTP-Binding Proteins
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LSG1 protein, S cerevisiae