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.
Greenberg
J R
JR
Department of Biology, University of Rochester, Rochester, New York 14627, USA.
Phan
L
L
Gu
Z
Z
deSilva
A
A
Apolito
C
C
Sherman
F
F
Hinnebusch
A G
AG
Goldfarb
D S
DS
D002455:Cell Division / Q000235:genetics; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D010303:Paromomycin / Q000494:pharmacology; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000378:metabolism*; D011132:Polyribosomes / Q000378:metabolism; D011485:Protein Binding; D012269:Ribosomal Proteins / Q000235:genetics; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013489:Suppression, Genetic
D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins; C077915:NIP1 protein, S cerevisiae; D009687:Nuclear Proteins; D010448:Peptide Initiation Factors; C045547:RPL39 protein, S cerevisiae; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D010303:Paromomycin