Abstract
In amino acid-starved yeast cells, inhibition of the guanine nucleotide exchange factor eIF2B by phosphorylated translation initiation factor 2 results in increased translation of GCN4 mRNA. We isolated a suppressor of a mutant eIF2B. The suppressor prevents efficient GCN4 mRNA translation due to inactivation of the small ribosomal subunit protein Rps31 and results in low amounts of mutant 40 S ribosomal subunits. Deletion of one of two genes encoding ribosomal protein Rps17 also reduces the amounts of 40 S subunits but does not suppress eIF2B mutations or prevent efficient GCN4 translation. Our findings show that Rps31-deficient ribosomes are altered in a way that decreases the eIF2B requirement and that the small ribosomal subunit mediates the effects of low eIF2B activity on cell viability and translational regulation in response to eIF2 phosphorylation.
Highlights
In amino acid-starved yeast cells, inhibition of the guanine nucleotide exchange factor eIF2B by phosphorylated translation initiation factor 2 results in increased translation of GCN4 mRNA
Translational regulation of GCN4 mRNA is mediated by four uORFs
The phenotypes of an rps31 disruption allele and the sup allele were indistinguishable with respect to GCN4 mRNA translation, amino acid analog sensitivity, suppression of gcd1505, and cold-sensitive growth (Table IV, wild-type compared with sup and rps31::HIS3 phenotypes, Table III rps31::HIS3)
Summary
(Received for publication, May 19, 1998, and in revised form, September 21, 1998). From the ‡Institute of Biochemistry and Molecular Biology, University of Berne, CH-3012 Berne, Switzerland, the §Laboratory of Eukaryotic Gene Regulation, NICHHD, National Institutes of Health, Bethesda, Maryland 20892, and ¶RDIF/GBF, National Research Institute for Biotechnology, Mascheroder Weg 1, D-38124 Braunschweig, Germany. In amino acid-starved yeast cells, inhibition of the guanine nucleotide exchange factor eIF2B by phosphorylated translation initiation factor 2 results in increased translation of GCN4 mRNA. The suppressor prevents efficient GCN4 mRNA translation due to inactivation of the small ribosomal subunit protein Rps and results in low amounts of mutant 40 S ribosomal subunits. Deletion of one of two genes encoding ribosomal protein Rps reduces the amounts of 40 S subunits but does not suppress eIF2B mutations or prevent efficient GCN4 translation. Our findings show that Rps31-deficient ribosomes are altered in a way that decreases the eIF2B requirement and that the small ribosomal subunit mediates the effects of low eIF2B activity on cell viability and translational regulation in response to eIF2 phosphorylation. Suppression is due to a mutation in the small subunit ribosomal protein gene RPS31 (previous designations UBI3 and RPS27A), providing evidence for an in vivo involvement of the ribosome in eIF2 recycling
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
