Abstract
The four nucleolar proteins NOP1, SSB1, GAR1, and NSR1 of Saccharomyces cerevisiae share a repetitive domain composed of repeat units rich in glycine and arginine (GAR domain). We have cloned and sequenced a fifth member of this family, NOP3, and shown it to be essential for cell viability. The NOP3 open reading frame encodes a 415 amino acid protein with a predicted molecular mass of 45 kD, containing a GAR domain and an RNA recognition motif. NOP3-specific antibodies recognize a 60-kD protein by SDS-PAGE and decorate the nucleolus and the surrounding nucleoplasm. A conditional lethal mutation, GAL::nop3, was constructed; growth of the mutant strain in glucose medium represses NOP3 expression. In cells depleted of NOP3, production of cytoplasmic ribosomes is impaired. Northern analysis and pulse-chase labeling indicate that pre-rRNA processing is inhibited at the late steps, in which 27SB pre-rRNA is cleaved to 25S rRNA and 20S pre-rRNA to 18S rRNA.
MeSH terms
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Amino Acid Sequence
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Base Sequence
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Cell Nucleolus / chemistry
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Cell Nucleus / chemistry
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Cloning, Molecular
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Fluorescent Antibody Technique
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Fungal Proteins / chemistry
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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Molecular Sequence Data
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Molecular Weight
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Mutation
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Nuclear Proteins / chemistry
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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RNA Precursors / metabolism*
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RNA Processing, Post-Transcriptional*
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RNA, Fungal / metabolism
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RNA-Binding Proteins*
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Ribosomes / metabolism
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Saccharomyces cerevisiae / chemistry*
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / physiology
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Saccharomyces cerevisiae Proteins*
Substances
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Fungal Proteins
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NPL3 protein, S cerevisiae
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Nuclear Proteins
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RNA Precursors
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RNA, Fungal
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RNA-Binding Proteins
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Saccharomyces cerevisiae Proteins
Associated data
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GENBANK/M74319
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GENBANK/M74320
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GENBANK/M74321
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GENBANK/M74322
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GENBANK/M74323
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GENBANK/M74324
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GENBANK/X66019
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GENBANK/X66084
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GENBANK/Z15036
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GENBANK/Z15040