Temperature-dependent mutational specificity of an Escherichia coli mutator, dnaQ49, defective in 3′→5′ exonuclease (proofreading) activity

Isbell, Roberta J.; Fowler, Robert G.

doi:10.1016/0027-5107(89)90146-2

Cited by 16 publications

(4 citation statements)

References 22 publications

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“…Among these base substitutions, A:T to G:C transitions are relatively frequent. 58 The two POLD1 mutations in DLD-1 and LoVo cells were G:C to A:T transitions, and the POLE mutation found in the IC678 tumour was also transition ( Table 2). On the other hand, MSH6 mutations in DLD-1 cells are a 1-bp deletion, that is, frameshift mutation, and a large sequence deletion/insertion.…”

Section: Discussionmentioning

confidence: 98%

Concurrent genetic alterations in DNA polymerase proofreading and mismatch repair in human colorectal cancer

et al. 2010

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Genomic sequences encoding the 3¢ exonuclease (proofreading) domains of both replicative DNA polymerases, pol delta and pol epsilon, were explored simultaneously in human colorectal carcinomas including six established cell lines. Three unequivocal sequence alterations, including one previously reported, were found, and all these were considered as dysfunctional mutations in light of the local amino-acid sequences. In particular, the F367S mutation found in the POLE gene encoding the pol epsilon catalytic subunit, which includes the proofreading domain, is the first found in human diseases. Surprisingly, the tumours carrying these proofreading domain mutations were all defective in DNA mismatch repair (MMR). In addition to the two cell lines with acknowledged MMR gene mutations, the third tumour was also demonstrated to harbour a distinct mutation in MLH1, and indeed exhibited a microsatellite-unstable phenotype. These findings suggest that, in concert with MMR deficiency, defective polymerase proofreading may also contribute to the mutator phenotype observed in human colorectal cancer. Our observations may suggest previously unrecognised complexities in the molecular abnormalities underlying the mutator phenotype in human neoplasms. Keywords: polymerase delta; polymerase epsilon; proofreading domain; colorectal cancer INTRODUCTION Mutation rates on the genome are invariably regulated and typically suppressed to an extremely low level, such as 10 À10 per base replicated, in the organisms. 1 The high fidelity of DNA replication is achieved by several molecular mechanisms. The frequency of erroneous nucleotide incorporation is indeed extremely low compared with that expected from base-pairing energetics, and the vast reduction of the misincorporation frequency involves three steps of molecular events: (a) correct incorporation of complementary nucleotides by DNA polymerases, (b) removal of the newly added nucleotides, particularly incorrectly paired nucleotides, by the 3¢ exonuclease activities associated with the DNA polymerases (proofreading) and (c) postreplicative scanning of mispaired bases by DNA mismatch repair (MMR). 2,3 Various Escherichia coli (E. coli) mutator strains have been used to study these molecular mechanisms by which organisms maintain their mutation rates at very low levels. The dnaQ + (mutD + ) gene of E. coli encodes the epsilon subunit of the DNA polymerase III holoenzyme that is involved in 3¢ exonuclease proofreading activity, 4 and, therefore, the mutation frequencies in the dnaQ mutators are sometimes 1000-10 000 times higher than the wild-type levels. 4,5 In E. coli, MMR is chiefly directed by the proteins encoded by the three genes: mutS + , mutL + and mutH + . 6 The mutS or mutL mutators exhibit an approximately 100 times increase in the mutation frequency. 7 Thus, polymerase proofreading and MMR are the two major

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Section: Discussionmentioning

confidence: 98%

Concurrent genetic alterations in DNA polymerase proofreading and mismatch repair in human colorectal cancer

et al. 2010

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“…We also found that dnaQ49 (V96G), a recessive allele known to have a strong mutator phenotype at 37°C but a moderate mutator effect at a lower temperature [37], confers a moderate mutator phenotype (20-fold; Table 2) at 28°C, indicating that the mutant ε protein must participate in replication to an appreciable extent in the presence of wild type ε at the lower temperature. As expected for a recessive allele, at 37°C dnaQ49 (V96G) barely elevated mutagenesis (<4 fold) in the dnaQ + background, and had no effect on SIVET induction (data not shown).…”

Section: Resultsmentioning

confidence: 78%

SOS induction and mutagenesis by dnaQ missense alleles in wild type cells

Gautam

Kalidindi

Humayun

2012

Mutation Research/Fundamental and Molecular Mechanisms of Mutag

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Mistranslation leads to elevated mutagenesis and replication arrest, both of which are hypothesized to result from the presence of mixed populations of wild type and mistranslated versions of DNA polymerase III subunit proteins. Consistent with this possibility, expression of missense alleles of dnaQ (which codes for the proofreading subunit ε in wild type (dnaQ+) cells is shown to lead to SOS induction as well as mutagenesis. Exposure to sublethal concentrations of streptomycin, an aminoglycoside antibiotic known to promote mistranslation, also leads to SOS induction.

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“…3A, direct correlations between mutation and transcription frequencies occur in both prokaryotes, such as a trpA E. coli auxotroph [12,36] and eukaryotes, e.g., the p53 tumor suppressor gene, [10,16], and a pre-B cell line [29,30]. In each case, the mutable bases are located in loops of identified secondary structures, as demonstrated in Fig.…”

Section: Correlations Between Mutation Frequencies Base Mutabilitmentioning

confidence: 99%

“…(B) Mutants of E. coli trpA auxotrophs located in a loop of SLS 4.9 [12,36]. Mutable codon 211 is highlighted in red to indicate its stability and location in SLS 4.9.…”

Section: Figmentioning

confidence: 99%

Kinetic models reveal the in vivo mechanisms of mutagenesis in microbes and man

Wright

Schmidt

Minnick

2013

Mutation Research/Reviews in Mutation Research

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This review summarizes the evidence indicating that mutagenic mechanisms in vivo are essentially the same in all living cells. Unique metabolic reactions to a particular environmental stress apparently target specific genes for increased rates of transcription and mutation, resulting in higher mutation rates for those genes most likely to solve the problem. Kinetic models which have demonstrated predictive value are described and are shown to simulate mutagenesis in vivo in E. coli, the p53 tumor suppressor gene, and somatic hypermutation. In all three models, direct correlations are seen between mutation frequencies and transcription rates. G and C nucleosides in single-stranded DNA (ssDNA) are intrinsically mutable, and G and C silent mutations in p53 and in VH framework regions provide compelling evidence for intrinsic mechanisms of mutability, since mutation outcomes are neutral and are not selected. During transcription, the availability of unpaired bases in the ssDNA of secondary structures is rate-limiting for, and determines the frequency of mutations in vivo. In vitro analyses also verify the conclusion that intrinsically mutable bases are in fact located in ssDNA loops of predicted secondary structures.

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Temperature-dependent mutational specificity of an Escherichia coli mutator, dnaQ49, defective in 3′→5′ exonuclease (proofreading) activity

Abstract: Isbell, Roberta J., "Temperature-dependent mutational specificity of an Escherichia coli mutator, dnaQ49, defective in 3'---> 5' exonuclease (proofreading) activity" (1989). Master's Theses. 3080.

Cited by 16 publications

References 22 publications

Concurrent genetic alterations in DNA polymerase proofreading and mismatch repair in human colorectal cancer

Concurrent genetic alterations in DNA polymerase proofreading and mismatch repair in human colorectal cancer

SOS induction and mutagenesis by dnaQ missense alleles in wild type cells

Kinetic models reveal the in vivo mechanisms of mutagenesis in microbes and man

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