Yeast NSR1 protein that has structural similarity to mammalian nucleolin is involved in pre-rRNA processing.
We have identified a yeast gene encoding a protein structurally similar to mammalian nucleolin. The gene was previously cloned as a cold shock-inducible gene and found to be identical to yeast NSR1 gene, which encodes a protein that has been reported to bind sequences required for nuclear localization of protein. The carboxyl-terminal half of NSR1, consisting of two tandemly repeated putative RNA-binding domains and a glycine/arginine-rich domain, has 37% amino acid sequence identity with the same part of mammalian nucleolin, while no sequence similarities are found between their amino-terminal regions. Although a null mutation of the NSR1 gene was not lethal, it caused a severe defect on growth. Pulse-labeling analysis revealed that the nsr1 strain had reduced levels of 18 S rRNA and accumulated 35 S pre-rRNA compared with the wild-type strain. The level of 25 S rRNA was also slightly reduced in the nsr1 strain. Pulse-chase labeling experiments showed slow processing of 35 S pre-rRNA and impaired methylation of 18 S rRNA. The ratio of 40 S to 60 S ribosomal subunits in the nsr1 strain is significantly reduced and is consistent with impaired synthesis of 18 S rRNA. The results indicate that NSR1 is involved in pre-rRNA processing and ribosome biosynthesis in yeast.
Kondo
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K
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey at Rutgers, Piscataway 08854-5635.
Inouye
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M
D000595:Amino Acid Sequence; D000818:Animals; D002872:Chromosome Deletion; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D005800:Genes, Fungal; D007700:Kinetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics*; D010750:Phosphoproteins / Q000235:genetics*; D011487:Protein Conformation; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D016601:RNA-Binding Proteins; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid; D000097796:Nucleolin
D005656:Fungal Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D000097796:Nucleolin; C068036:NSR1 protein, S cerevisiae