Inactivation of the yeast Sen1 protein affects the localization of nucleolar proteins

Mol Gen Genet. 1995 Dec 20;249(6):571-84. doi: 10.1007/BF00418026.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Biological Transport
  • Cell Compartmentation*
  • Cell Nucleolus / metabolism*
  • Cell Nucleus / metabolism
  • DNA Helicases
  • Fluorescent Antibody Technique, Indirect
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Genes, Fungal
  • HSP70 Heat-Shock Proteins
  • Molecular Sequence Data
  • Mutation
  • Nuclear Proteins / metabolism
  • RNA Helicases
  • RNA Ligase (ATP) / deficiency
  • RNA Precursors / metabolism
  • RNA Splicing
  • RNA, Transfer / metabolism
  • Ribonucleoproteins, Small Nucleolar*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins*
  • Sequence Deletion
  • Structure-Activity Relationship

Substances

  • Fungal Proteins
  • HSP70 Heat-Shock Proteins
  • NOP1 protein, S cerevisiae
  • Nuclear Proteins
  • RNA Precursors
  • Ribonucleoproteins, Small Nucleolar
  • SSB1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • RNA, Transfer
  • SEN1 protein, S cerevisiae
  • DNA Helicases
  • RNA Helicases
  • RNA Ligase (ATP)