The nucleotide sequence of the first externally suppressible-1 frameshift mutant, and of some nearby leaky frameshift mutants.

Abstract

Nine mutants within a 23 nucleotide sequence of the trpE gene of Salmonella typhimurium have been characterized. trpE91, a mutant which is externally suppressible has a single base deletion. Eight (or nine) nucleotides upstream of this deletion, two independently isolated mutations have the same transversion. In combination with trpE91 these mutations lead to partial restoration of synthesis of anthranilate synthetase in the absence of external suppressors. In the transversion the sequence A CA is changed to A AA and this new sequence may be the site where frameshifting occurs to allow leakiness. Leakiness is displayed by two further mutants of the same sign as trpE91, and one of the opposite sign, in the absence of any base substitution or external suppressors. Specific sequences, e.g., UUUC, may be especially prone to frameshifting and this sequence is created at the site of the +1 frameshift mutant which displays leakiness. In the new reading frame generated by the two ‐1 frame leaky mutants, a tryptophan codon is encountered. Leakiness is necessarily detected in the absence of tryptophan and under these conditions there will be a shortage of charged tryptophan tRNA. The possibility of such functional imbalance leading to frameshifting in these mutants is discussed.

Identification of the mob Genes of Plasmid pSC101 and Characterization of a Hybrid pSC101-R1162 System for Conjugal Mobilization

“…At the site for termination of translation, the RNA has the sequence UUU UUC UAA. This is a particularly "slippery" sequence, causing Ϫ1 frameshifts (1,15), which would then place translation in the correct reading frame for the downstream pSC101 mobA fragment. In any case, it is important to note that the functional unit represented by the pSC101 mobA fragment is distinct from the cleavage-ligation domain of MobA and, at the very least, can be separated from it by a polypeptide bridge.…”

tRNA hopping: enhancement by an expanded anticodon

“…All of the hopR alleles studied here were isolated as external suppressors of the -1 frameshift mutation, trpE91 in E. coli (Atkins et al, 1983;Hughes et al, 1989). In order to study the decoding specificity of hopR, specific lacZ mutations have been constructed by cloning synthetic, complementary oligonucleotides into the 5' region of a plasmid-bome ,3-galactosidase gene (Weiss et al, 1987 (Yokoyama et al, 1985).…”

Overproduction of release factor reduces spontaneous frameshifting and frameshift suppression by mutant elongation factor Tu

“…Three leaky frameshift mutations in the trp operon were tested. Each of these mutations, trpE871 (+1) trpE873 (-1), and trpE879 (-1), has a frameshift window ending in UGA (1,31). The four test plasmids were introduced into each strain (TH420, TH422, TH432), and growth in the absence of tryptophan was assayed.…”