Phase-shift and other mutants in the first part of the<i>r</i>II B cistron of bacteriophage T4

Barnett, Leslie; Brenner, Sydney; Crick, Francis; Shulman, R. G.; Watts‐Tobin, R. J.

doi:10.1098/rstb.1967.0030

Cited by 86 publications

(6 citation statements)

References 19 publications

(3 reference statements)

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“…The NH2 terminus of the rIIB protein is particularly well suited for the examination of frameshift specificity (6,7,(11)(12)(13). Two of its characteristics were crucial to our test of the mutational model: the presence of quasipalindromes in the DNA sequence that predict frameshifts (3,6,11) and genetic properties that permit the selection of frameshift mutations in this region of the rIB gene by methods that do not select against predicted base substitutions (13).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Demonstration of the production of frameshift and base-substitution mutations by quasipalindromic DNA sequences.

Boer¹,

Ripley²

1984

Proc. Natl. Acad. Sci. U.S.A.

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The in vivo production of frameshift and base-substitution mutations predicted as a consequence of the metabolic processing of misaligned quasipalindromic DNA sequences has been confirmed. Spontaneous frameshift mutations of the T4 Wi gene that had been genetically mapped to quasipalindromic DNA sequences were sequenced. Some of the mutant sequences are exactly those predicted by a mutational model based on misaligned quasipalindromes. Furthermore, these sequences are distinct from those predicted by the classical frameshift model based on misaligned repeated sequences. The ilI frameshift mutant sequences reported here result from the deletion of a specific base or bases that would remain looped out should the quasipalindromes assume a hairpin secondary structure. One hairpin predicted not only the deletion of two bases (a frameshift) but the concomitant production of nearby but noncontiguous base substitutions. The substitution of as many as three bases as well as the frameshift were predicted to arise as a consequence of a single mutational event in the palindrome. Two independent examples of the predicted deletion frameshift were found among the small sample of sequenced spontaneous frameshifts examined and both were associated with the predicted transversion and transition base substitutions.Frameshift mutations often result from the addition or deletion of a repeating unit of a repeated DNA sequence. Metabolic processing of misaligned pairing between one of the repeating units and the complement of another is believed to be responsible (1, 2). However, frameshifts can occur in DNA sequences that are not repeated. A consideration of molecular mechanisms responsible for these mutations led to the proposal that some frameshifts occur because of processing of misaligned pairing mediated by quasipalindromes (3-5).Palindromic sequences permit the formation of alternative DNA secondary structures such as DNA hairpins. The action of ordinary DNA metabolism on such structures is predicted to lead to mutation (3, 5). The demonstration of mutations predicted to occur as a consequence of such processing and not by other mutational models would be strong confirmation of the quasipalindrome mutational model and would suggest the occurrence of palindromically mediated misalignments in vivo.Quasipalindromes permit the formation of misaligned structures through the self-complementarity of their palindromic portions and provide templates for base-substitution and frameshift mutations in their nonpalindromic portions (3). Mutations are predicted to result from templated processes that replace bases residing in one half of the hairpin with bases complementary to the other half. The predicted mutations can be readily visualized by examining quasipalindromic DNA sequences in hairpin structures (Fig. 1). Each unpaired base in the stem of the hairpin lacks a complemen-

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Section: Resultsmentioning

confidence: 99%

“…These bases mark the positions of out-of-frame termination codons (barriers B4 and B6) that can be identified genetically (4,6,13). Spontaneous frameshifts mapping to this region (7) were cloned into M13 and sequenced.…”

Section: Resultsmentioning

confidence: 99%

Demonstration of the production of frameshift and base-substitution mutations by quasipalindromic DNA sequences.

Boer¹,

Ripley²

1984

Proc. Natl. Acad. Sci. U.S.A.

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“…We used the phage T4 rIIA and rIIB genes to search for the presumed site on mRNA that responds to inhibition byregA+ gene function. These two T4 genes are ideal for such studies because (i) they are well-characterized genetically (29)(30)(31),.…”

mentioning

confidence: 99%

“…T4 regA mutations do not affect RNA synthesis, although the protein overproduction ofT4 regA-phage infections is accompanied by a prolonged functional lifetime for the corresponding mRNA (and by decreased breakdown of some phage RNA) (23,24,27,28 The T4 rIB gene product is one of the phage proteins that are hyperproduced in T4 regA-phage infections. We tested several precisely mapped missense, nonsense, frameshift, and deletion mutations of the rIIB gene (7,(29)(30)(31) The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.…”

mentioning

confidence: 99%

Translational regulation: identification of the site on bacteriophage T4 rIIB mRNA recognized by the regA gene function.

Karam¹,

Gold²,

Singer³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

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The bacteriophage T4 gene regA encodes a protein that diminishes the expression of many unlinked early T4 genes. Previous work demonstrated that regA-mediated repression occurs after transcription. We report here on the identification of the target site on one regA-sensitive mRNA, the message encoding the phage T4 rUB protein. The target for regA-mediated action overlaps the translational initiation domain of the rIB messenger. The regA protein may be a repressor that operates translationally on a significant and interesting set of early phage T4 mRNAs.Evidence has accumulated over the last several years for control ofprokaryotic gene expression beyond the level oftranscription. Several factors may influence the translational yield from specific transcripts: discrimination by ribosomes in selecting one transcript over others, regulation of translation of particular mRNAs by repressors or activators, and destruction of transcripts at nonuniform rates. Direct evidence exists (in different systems) for all but one of these control mechanisms (1). The intrinsic strength of a ribosome binding site (refs. 1-7) determines the constitutivet level of specific translation, whereas regulation might encompass a reversible and specific repression or activation of translation through the intervention of a regulatory molecule. Alteration of transcripts by an RNase may be specific and, therefore, an example of irreversible regulation (8, 9). Reports of regulation of translation are rare: (i) the Escherichia coli RNA phages utilize translational regulation (10-14), (ii) the bacteriophage T4 controls the expression of its major DNA binding protein through autogenous translational regulation (15-18), and (iii) translational regulation is responsible for the careful titration of the quantities of several ribosomal proteins in E. coli (19)(20)(21)(22). Compared with the abundant descriptions oftranscriptional regulation, the literature on prokaryotic translational control is not vast.Recently, a phage T4 function was discovered that plays a role in control of the translation of a number of phage transcripts. Mutations in the regA gene of T4 lead to overproduction of a small number of the proteins that are synthesized during the early stages of phage development (23)(24)(25)(26)(27). The effects of these mutations seem to be mediated by loss ofa diffusible substance, probably a protein (26). Some observations suggest that the regA protein functions at a posttranscriptional level. T4 regA mutations do not affect RNA synthesis, although the protein overproduction ofT4 regA-phage infections is accompanied by a prolonged functional lifetime for the corresponding mRNA (and by decreased breakdown of some phage RNA) (23,24,27,28 The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. 4670Biochemistry: Karam et al.Measurement of Phage T4 rUB Protein Synthesis. The methods for label...

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“…Results from the same laboratory (18) show that reading frame shifts caused by a mutant tRNA, hopRI, are greatly enhanced when the "take-off' site is followed by a stop codon (UAA and UAG were tested). Each of these studies (3,18,29) suggests that nonsense codons can be associated with enhanced levels of frameshifting.…”

Section: Suppression Of the Frameshift Mutation Trpe91 By Tufa8mentioning

confidence: 99%

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

Aulin¹,

Hughes²

1990

J Bacteriol

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Mutant forms of elongation factor Tu encoded by tufA8 and tufB103 in Salmonella typhimurium cause suppression of some but not all frameshift mutations. All of the suppressed mutations in S. typhimurium have frameshift windows ending in the termination codon UGA. Because both tufA8 and tuJB103 are moderately efficient UGA suppressors, we asked whether the efficiency of frameshifting is influenced by the level of misreading at UGA. We introduced plasmids synthesizing either one of the release factors into strains in which the tuf mutations suppress a test framesilift mutation. We found that overproduction of release factor 2 (which catalyzes release at UGA and UAA) reduced frameshifting promoted by the tuf mutations at all sites tested. However, at one of these sites, tpE91, overproduction of release factor 1 also reduced suppression. The spontaneous level of frameshift "leakiness" at three sites in trpE, each terminating in UGA, was reduced in strains carrying the release factor 2 plasmid. We conclude that both spontaneous and suppressor-enhanced reading-frame shifts are influenced by the activity of peptide chain release factors. However, the data suggest that the effect of release factor on frameshifting does not necessarily depend on the presence of the normal triplet termination signal.

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Phase-shift and other mutants in the first part of therII B cistron of bacteriophage T4

Cited by 86 publications

References 19 publications

Demonstration of the production of frameshift and base-substitution mutations by quasipalindromic DNA sequences.

Demonstration of the production of frameshift and base-substitution mutations by quasipalindromic DNA sequences.

Translational regulation: identification of the site on bacteriophage T4 rIIB mRNA recognized by the regA gene function.

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

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