DNA polymerase ε and δ proofreading suppress discrete mutator and cancer phenotypes in mice

Albertson, Tina; Ogawa, Masanori; Bugni, James M.; Hays, Laura E.; Chen, Yang; Wang, Yanping; Treuting, Piper M.; Heddle, John A.; Goldsby, Robert E.; Preston, Bradley D.

doi:10.1073/pnas.0907147106

Cited by 206 publications

(241 citation statements)

References 34 publications

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“…Indeed, in the yeast mutants in which pol delta or epsilon proofreading is selectively inactivated, the mutations rates are 10-100 times higher than the wild-type strains. [26][27][28] Recently, mice carrying artificial alleles with substitutions at essential amino-acid residues in the proofreading domains of pol delta 29,30 and epsilon 31 have been reported. The observed mutation rates were indeed significantly elevated over the wild-type levels.…”

Section: Introductionmentioning

confidence: 99%

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: Introductionmentioning

confidence: 99%

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

et al. 2010

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“…A homozygous knockout of these polymerases results in embryonic lethality [Overbeek et al, 2011;Glodsby et al, 2001Glodsby et al, , 2002Uchimura et al, 2009]. Defects in the exonuclease proofreading activity result in increased incidence of malignancies and cardiac abnormalities [Goldsby et al, 2001[Goldsby et al, , 2002Albertson et al, 2009;Uchimura et al, 2009]. Defects in the polymerase activity of Pol d resulted in an increased incidence of cancer and cardiomyopathy [Venkatesan et al, 2007].…”

Section: The B Family Of Dna Polymerasesmentioning

confidence: 99%

“…In the case of Pole e /Mlh1 mice, homozygous mutant mice were present at normal ratios upto E14.5 but none survived after weaning. The Pole e /Msh2 homozygous mutation resulted in complete postnatal lethality with no mice surviving at weaning [Albertson et al, 2009].…”

Section: Dna Polymerase Epsilon (Pol E)mentioning

confidence: 99%

Mouse models of DNA polymerases

Menezes¹,

Sweasy²

2012

Environ and Mol Mutagen

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In 1956, Arthur Kornberg discovered the mechanism of the biological synthesis of DNA and was awarded the Nobel Prize in Physiology or Medicine in 1959 for this contribution, which included the isolation and characterization of Escherichia coli DNA polymerase I. Now there are 15 known DNA polymerases in mammalian cells that belong to four different families. These DNA polymerases function in many different cellular processes including DNA replication, DNA repair, and damage tolerance. Several biochemical and cell biological studies have provoked a further investigation of DNA polymerase function using mouse models in which polymerase genes have been altered using gene-targeting techniques. The phenotypes of mice harboring mutant alleles reveal the prominent role of DNA polymerases in embryogenesis, prevention of premature aging, and cancer suppression. Environ. Mol. Mutagen. 53:645-665, 2012. V V C 2012 Wiley Periodicals, Inc.

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“…4 Furthermore, tumors with POLE exonuclease lacked MLH1 silencing, which is consistent with findings from mouse models that POLE EDMs are mutually exclusive and are incompatible with the complete loss of mismatch repair (MMR). 6 However, it has been reported that several endometrial and colon tumors with POLE EDMs harbor mutations in MMR genes, although the functional significance of these mutations is uncertain, particularly in the setting of an MSS phenotype. 4 In this issue of Cancer, Billingsworth and colleagues present data challenging the notion that POLE EDMs are associated with an MSS phenotype in endometrial cancer.…”

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confidence: 99%

“…Although POLE mutations were significantly more common in MSI tumors that lacked MLH1 methylation, the authors reported 4 tumors with both POLE mutations and MLH1 silencing; this was an unexpected finding, because previous reports have suggested that MLH1 silencing and POLE EDMs are mutually exclusive. 4,6 POLE EDMs were identified in 8 MSI tumors without MLH1 silencing, and the authors examined 3 of these tumors using immunohistochemistry (IHC) for DNA MMR protein expression. Two of the 3 tumors lacked 1 or more MMR proteins and harbored somatic mutS homolog 6 (MSH6) mutations but had no germline MMR mutations.…”

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confidence: 99%

POLE mutations as an alternative pathway for microsatellite instability in endometrial cancer: Implications for Lynch syndrome testing

Konstantinopoulos

Matulonis

2014

Cancer

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Further elucidation of the genomics of endometrial cancer has the capability and promise of much needed understanding of causative factors of this disease and its hereditary predisposition, development of more effective therapeutics, and improved predictive indicators for use of chemotherapy and radiation therapy. Significant strides toward these goals have been accomplished by The Cancer Genome Atlas (TCGA) project, which has genomically characterized and distilled endometrial cancer into 4 major groups based on microsatellite instability (MSI), somatic copy number alterations (SCNAs), and somatic nucleotide substitutions. 1 These groups include: 1) an ultramutated group with a unique nucleotide change spectrum of increased cysteine-toalanine (C!A) transversion frequency; 2) a hypermutated group of cancers with MSI, most of which had mutL homolog 1 (MLH1) promoter methylation (MSI group); 3) a group of cancers with microsatellite stability (MSS) that had a relatively lower mutation frequency and low SCNAs; and 4) a serous-like group comprised of cancers with serous or mixed histology and a few high-grade endometrioid cancers, all of which harbored extensive SCNAs and a low mutation rate. 1 The ultramutated group included 17 tumors (7% of all tumors in the TCGA data set), all of which harbored mutations in the exonuclease domain of polymerase e (POLE), and was associated with improved progression-free survival (PFS) compared with all other groups, and the largest difference was observed when this ultramutated group was compared with the serous-like group.POLE and polymerase d (POLD1) belong to the B family of polymerases and are responsible for synthesizing the leading and lagging strands in eukaryotic DNA replication. 2 POLE and POLD1 form the major catalytic and proofreading units of Pole and Pold enzyme complexes, which ensure the high fidelity of DNA replication. Both POLE and POLD1 exhibit the greatest homology over their proofreading exonuclease domain (residues 268-471 and 304-517, respectively), which exhibit a high level of evolutionary conservation. It is estimated that their proofreading 3 0 to 5 0 exonuclease activity, which locates and replaces erroneous bases in the daughter strand, helps protect against genomic instability by improving the fidelity of DNA replication by at least 10-fold. 3 Several cancer genome sequencing efforts have consistently demonstrated that a small fraction of colorectal and endometrial cancers contain somatic mutations within the exonuclease domains of POLE (3% and 7% in the TCGA colorectal and uterine projects, respectively). 1,4 Contrary to POLE, very few somatic POLD1 exonuclease domain mutations (EDMs) have been detected in human cancers, whereas both germline POLD1 and POLE mutations have been reported in association with a high risk of multiple colorectal adenomas and carcinomas, whereas germline POLD1 mutations also predispose to endometrial cancers. 5 Somatic POLE EDMs in endometrial and colorectal cancers have demonstrated significant overlap; and codons 286 (a c...

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DNA polymerase ε and δ proofreading suppress discrete mutator and cancer phenotypes in mice

Cited by 206 publications

References 34 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

Mouse models of DNA polymerases

POLE mutations as an alternative pathway for microsatellite instability in endometrial cancer: Implications for Lynch syndrome testing

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