Nip1p associates with 40 S ribosomes and the Prt1p subunit of eukaryotic initiation factor 3 and is required for efficient translation initiation

J Biol Chem. 1998 Sep 4;273(36):23485-94. doi: 10.1074/jbc.273.36.23485.

Abstract

Nip1p is an essential Saccharomyces cerevisiae protein that was identified in a screen for temperature conditional (ts) mutants exhibiting defects in nuclear transport. New results indicate that Nip1p has a primary role in translation initiation. Polysome profiles indicate that cells depleted of Nip1p and nip1-1 cells are defective in translation initiation, a conclusion that is supported by a reduced rate of protein synthesis in Nip1p-depleted cells. Nip1p cosediments with free 40 S ribosomal subunits and polysomal preinitiation complexes, but not with free or elongating 80 S ribosomes or 60 S subunits. Nip1p can be isolated in an about 670-kDa complex containing polyhistidine-tagged Prt1p, a subunit of translation initiation factor 3, by binding to Ni2+-NTA-agarose beads in a manner completely dependent on the tagged form of Prt1p. The nip1-1 ts growth defect was suppressed by the deletion of the ribosomal protein, RPL46. Also, nip1-1 mutant cells are hypersensitive to paromomycin. These results suggest that Nip1p is a subunit of eukaryotic initiation factor 3 required for efficient translation initiation.

Publication types

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

MeSH terms

  • Cell Division / genetics
  • Eukaryotic Initiation Factor-3
  • Fungal Proteins / metabolism*
  • Mutation
  • Nuclear Proteins / metabolism*
  • Paromomycin / pharmacology
  • Peptide Chain Initiation, Translational*
  • Peptide Initiation Factors / metabolism*
  • Polyribosomes / metabolism
  • Protein Binding
  • Ribosomal Proteins / genetics
  • Ribosomes / metabolism*
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins*
  • Suppression, Genetic

Substances

  • Eukaryotic Initiation Factor-3
  • Fungal Proteins
  • NIP1 protein, S cerevisiae
  • Nuclear Proteins
  • Peptide Initiation Factors
  • RPL39 protein, S cerevisiae
  • Ribosomal Proteins
  • Saccharomyces cerevisiae Proteins
  • Paromomycin