Mutational analysis of the Prt1 protein subunit of yeast translation initiation factor 3.
The Saccharomyces cerevisiae PRT1 gene product Prt1p is a component of translation initiation factor eIF-3, and mutations in PRT1 inhibit translation initiation. We have investigated structural and functional aspects of Prt1p and its gene. Transcript analysis and deletion of the PRT1 5' end revealed that translation of PRT1 mRNA is probably initiated at the second in-frame ATG in the open reading frame. The amino acid changes encoded by six independent temperature-sensitive prt1 mutant alleles were found to be distributed throughout the central and C-terminal regions of Prt1p. The temperature sensitivity of each mutant allele was due to a single missense mutation, except for the prt1-2 allele, in which two missense mutations were required. In-frame deletion of an N-terminal region of Prt1p generated a novel, dominant-negative form of Prt1p that inhibits translation initiation even in the presence of wild-type Prt1p. Subcellular fractionation suggested that the dominant-negative Prt1p competes with wild-type Prt1p for association with a component of large Prt1p complexes and as a result inhibits the binding of wild-type Prt1p to the 40S ribosome.
Evans
D R
DR
Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada.
Rasmussen
C
C
Hanic-Joyce
P J
PJ
Johnston
G C
GC
Singer
R A
RA
Barnes
C A
CA
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins / Q000235:genetics* / Q000494:pharmacology; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects; D010446:Peptide Fragments / Q000494:pharmacology; D010448:Peptide Initiation Factors / Q000235:genetics* / Q000494:pharmacology; D011110:Polymorphism, Genetic; D039665:Prokaryotic Initiation Factor-3; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012322:RNA Precursors / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D014158:Transcription, Genetic
D039621:Eukaryotic Initiation Factor-3; D005656:Fungal Proteins; D046911:Macromolecular Substances; D010446:Peptide Fragments; D010448:Peptide Initiation Factors; D039665:Prokaryotic Initiation Factor-3; D011500:Protein Synthesis Inhibitors; C050998:Prt1 protein, S cerevisiae; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins