Sequence and functional similarity between a yeast ribosomal protein and the Escherichia coli S5 ram protein.

Abstract

The accurate and efficient translation of proteins is of fundamental importance to both bacteria and higher organisms. Most of our knowledge about the control of translational fidelity comes from studies of Escherichia coli. In particular, ram (ribosomal ambiguity) mutations in structural genes of E. coli ribosomal proteins S4 and S5 have been shown to increase translational error frequencies. We describe the first sequence Analyses of informational suppressors in Escherichia coli have elucidated the components involved in determining the fidelity of translation. In most instances, the factors identified have been either tRNAs or ribosomal proteins (31,69,84). Alterations in five different ribosomal proteins have been shown to influence translational accuracy. Mutations in the structural genes for S12 (30), S17 (8), and L6 (53) can cause an increase in accuracy, while mutations in the structural genes for L7/L12 (47), S4 (77), and S5 (13, 71) can decrease fidelity. Such mutations that affect S4 or S5 are known as ram (ribosomal ambiguity) mutations because they cause a general ambiguity of translation, suppressing nonsense as well as missense and frameshift mutations (3, 73). More recently, nonsense suppressor phenotypes have also been shown to be associated with mutations in elongation factor EF-Tu (85, 89).We and others have used a similar genetic approach to identify components of the eucaryotic protein synthesis machinery that control translational fidelity (2,21,25,54,65,88,91,95 sup45, SUP44, and SUP46 strains increase in vitro misreading of polyuridylate templates (25,62).Despite the suggestive biochemical evidence, the first two yeast omnipotent suppressor genes to be cloned and sequenced (SUP35+ and SUP45+) do not encode ribosomal proteins (10,11,17,18,38,54,57,95). The SUP45+ gene is predicted to encode a protein of molecular mass 49 kDa (10). Regions of weak similarity to several tRNA synthetases were found, but the function of the gene product is still not known. The SUP35+ gene is predicted to encode a protein of 76.5 kDa that shows a high degree of similarity to EF-la (45, 54, 95) but is not identical to any of the three biochemically characterized elongation factors from yeast cells. Neither SUP35+ nor SUP45+ appears likely to encode a ribosomal protein, since both predicted gene products are much larger than ribosomal proteins, and their codon usage patterns indicate that, unlike ribosomal protein genes, they are not highly expressed (10,54,95).Here, we describe the sequence of a third yeast omnipotent suppressor gene, sup44+. This suppressor does encode a ribosomal protein. Furthermore, the SUP44 protein shows substantial sequence similarity to the E. coli S5 ram protein. MATERIALS AND METHODSStrains and genetic methods. The following Saccharomyces cerevisiae strains were used: SL815-26B [et met8-J leu2-1 trpl-J (his5-2 and/or his3-J) Iys2-J ura3-52 SUP44] and SL-982 [ala ura3-521ura3-52 met8-J/met8-J leu2-111eu2-1 ade3-261+ his5-21+ his3-All+ tyr7-J1+ trpl-l1+]. Standard yeast genetic procedu...

Nip1p Associates with 40 S Ribosomes and the Prt1p Subunit of Eukaryotic Initiation Factor 3 and Is Required for Efficient Translation Initiation

“…Two of the suppressor genes, SUP35 and SUP45, code for termination factors (53)(54)(55). SUP44 codes for a small subunit ribosomal protein (56). As far as we know, paromomycin sensitivity has not been reported previously for mutant initiation factors.…”

Selective translational control and nonspecific posttranscriptional regulation of ribosomal protein gene expression during development and regeneration of rat liver.

“…Conceivably, the TLRE reacts with a specific factor, which is quantitatively regulated or qualitatively modified in response to changes in cellular growth rate. Presumably, binding of this factor to the TLRE prevents or enhances the interaction of rp mRNAs with ribosomes and other compo- (3,28). Nonetheless, unlike the selective translational control of rp mRNAs, the reduction in their abundance during liver development seems to be a part of a general inhibitory effect, which includes many other housekeeping mRNAs.…”

Human Inter-α-Trypsin Inhibitor Heavy Chain H3 Gene

“…The primordial ITIH4 then acquired exon 1 (homologous to the transcriptional activator hepatocyte nuclear factor 6 (52)) and the 3Ј end sequences (homologous to the highly conserved repetitive mouse gene designated llrep3) to produce the ITIH4 gene. The llrep3 gene has a propensity to form pseudogenes in mammals (53) and is closely related to the yeast omnipotent informational suppressor sup44 which encodes the yeast ribosomal protein S4 (54) and the ribosomal protein S2 gene in human tumors (55). The presence of the 3Ј end of ITIH4 in this region of chromo- -competitor (lanes 3-5), H1 RE (lanes 6 -8), and C/EBP Bakker (lanes 9 -11).…”