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

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.
Mesh Terms:
Cell Division, Eukaryotic Initiation Factor-3, Fungal Proteins, Mutation, Nuclear Proteins, Paromomycin, Peptide Chain Initiation, Translational, Peptide Initiation Factors, Polyribosomes, Protein Binding, Ribosomal Proteins, Ribosomes, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Suppression, Genetic
J. Biol. Chem.
Date: Sep. 04, 1998
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