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Mol. Cell. Biol., Aug 1995, 4525-4535, Vol 15, No. 8
DR Evans, C Rasmussen, PJ Hanic-Joyce, GC Johnston, RA Singer and CA Barnes
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.
Copyright © 1995, American Society for Microbiology
Mutational analysis of the Prt1 protein subunit of yeast translation initiation factor 3
Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada.
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