Inactivation of the yeast Sen1 protein affects the localization of nucleolar proteins.
A mutation in the Saccharomyces cerevisiae SEN1 gene causes accumulation of end-matured, intron-containing pre-tRNAs. Cells containing the thermosensitive sen1-1 mutation exhibit reduced tRNA splicing endonuclease activity. However, Sen1p is not the catalytic subunit of this enzyme. We have used Sen1p-specific antibodies for cell fractionation studies and immunofluorescent microscopy and determined that Sen1p is a low abundance protein of about 239 kDa. It localizes to the nucleus with a granular distribution. We verified that a region in SEN1 containing a putative nuclear localization signal sequence (NLS) is necessary for nuclear targeting. Furthermore, we found that inactivation of Sen1p by temperature shift of a strain carrying sen1-1 leads to mislocalization of two nucleolar proteins, Nop1 and Ssb1. Possible mechanisms are discussed for several related nuclear functions of Sen1p, including tRNA splicing and the maintenance of a normal crescent-shaped nucleolus.
Laboratory of Genetics, University of Wisconsin, Madison 53706, USA.
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DeMarini
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D000595:Amino Acid Sequence; D001692:Biological Transport; D002451:Cell Compartmentation; D002466:Cell Nucleolus / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D004265:DNA Helicases; D019084:Fluorescent Antibody Technique, Indirect; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D018840:HSP70 Heat-Shock Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D020365:RNA Helicases; D011130:RNA Ligase (ATP) / Q000172:deficiency; D012322:RNA Precursors / Q000378:metabolism; D012326:RNA Splicing; D012343:RNA, Transfer / Q000378:metabolism; D020718:Ribonucleoproteins, Small Nucleolar; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D013329:Structure-Activity Relationship
D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; C064793:NOP1 protein, S cerevisiae; D009687:Nuclear Proteins; D012322:RNA Precursors; D020718:Ribonucleoproteins, Small Nucleolar; C095192:SSB1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D012343:RNA, Transfer; C542347:SEN1 protein, S cerevisiae; D004265:DNA Helicases; D020365:RNA Helicases; D011130:RNA Ligase (ATP)