Mutants of elongation factor Tu promote ribosomal frameshifting and nonsense readthrough.

Abstract

This is the first report of ribosomal frameshifting promoted by mutants of the elongation factor Tu (EF‐Tu). EF‐Tu mutants can suppress both −1 and +1 frameshift mutations. The level of nonsense readthrough is also increased at some UGA (this paper) and UAG (Hughes, 1987) sites by these mutants. Suppression occurs when a mutant tuf allele is paired with a wild‐type copy of the other tuf gene but is most efficient when both tuf genes are mutant. Frameshifting mediated by the tuf alleles studied, tufA8 and tufB103, is not general; indeed most frameshift mutations are not suppressed. Several possible mechanisms by which mutant EF‐Tu may cause frameshifting are discussed.

Antisense inhibition of the PTI-1 oncogene reverses cancer phenotypes

“…It was considered essential to determine if the effects on colony formation observed with the 1.9-kb AS PTI-1 gene were specific for this molecule or if a phenotypic response could also be induced with the AS 5Ј UTR or AS Trun-EF regions of PTI-1. This was of particular relevance because the Trun-EF might alter the expression or functionality of endogenous EF-1␣, thereby causing a nonspecific negative effect on protein synthesis and cell growth in cells not expressing PTI-1 (16)(17)(18)(19)(20)(21). To approach this question, a 500-bp region of the 5Ј UTR and the Trun-EF of PTI-1 were subcloned in an AS orientation into the pZeoSV vector and transfected into CREF-Trans 6, CREF-Trans 6:4 NMT, and DU-145 cells.…”

“…On the basis of studies in bacteria (elongation factor Tu) and yeast (EF-1␣), a model of action of EF-Tu͞EF-1␣ has been proposed (16)(17)(18)(19)(20)(21)35). These molecules are perceived to mediate the process of kinetic protein proofreading that controls appropriate codon-anticodon binding interactions (16).…”

“…These molecules are perceived to mediate the process of kinetic protein proofreading that controls appropriate codon-anticodon binding interactions (16). Specific mutations in EF-Tu elicit dominant-negative inhibition of protein synthesis and increase missense error rates in bacteria (16)(17)(18)(19). Similarly, mutations (specific amino acid and altered expression) in EF-1␣ in yeast directly affect frequencies of frameshifting and amino acid misincorporation, proofreading of codon-anticodon interactions, and suppression of nonsense mutations (20,21).…”

A single amino acid substitution in elongation factor Tu disrupts interaction between the ternary complex and the ribosome

“…Growth rates were measured in liquid M9 salts supplemented with glucose (0.4%, wt/vol) and tryptophan (10 mM) by inoculating 100 1.l of an overnight culture into 20 ml of fresh medium in a 300-ml flask, aerating the mixture by vigorous shaking, and measuring the increase in optical density of the culture as a function of time. Suppression of the trpE91 and hisG3720 mutations was measured as the time taken to form colonies on M9 minimal medium agar (24). Suppression of nonsense mutations in the lacI part of a lacIZ fusion was determined by measuring f3-galactosidase activity and normalizing it to the activity from a nonmutated fusion in the same strain (22).…”

Amber (UAG) suppressors affected in UGA/UAA‐specific polypeptide release factor 2 of bacteria: genetic prediction of initial binding to ribosome preceding stop codon recognition

“…Most of the translational suppressors that have been studied over the last three decades or so have been tRNAs that acquired an anticodon cognate to the termination codon; however other translational macromolecules are now coming under scrutiny. Non-sense suppression can be caused by mutations that affect the ribosome (reviewed by Murgola 1995) on the translation factors (Hughes et al 1987; reviewed by Hinnebusch & Liebman 1991). Irrespective of whether tRNA, ribosome or translation factors become a non-sense-suppressor, they must compete with the normal termination mechanism.…”