Translesion DNA Synthesis Catalyzed by Human Pol eta  and Pol kappa  across 1,N6-Ethenodeoxyadenosine*

Robert L. LevineDagger , Holly MillerDagger , Arthur GrollmanDagger , Eiji Ohashi§, Haruo Ohmori§, Chikahide Masutani, Fumio Hanaoka, and Masaaki MoriyaDagger ||

From the Dagger  Laboratory of Chemical Biology, Department of Pharmacological Sciences, State University of New York, Stony Brook, New York 11794-8651, the § Laboratory of Genetic Information Analysis, Department of Genetics and Molecular Biology, Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan, and the  Institute for Molecular and Cellular Biology, Osaka University, Suita, Osaka 565-0871, Japan

Received for publication, March 9, 2001


    ABSTRACT
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ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

1,N6-Ethenodeoxyadenosine, a DNA adduct generated by exogenous and endogenous sources, severely blocks DNA synthesis and induces miscoding events in human cells. To probe the mechanism for in vivo translesion DNA synthesis across this adduct, in vitro primer extension studies were conducted using newly identified human DNA polymerases (pol) eta  and kappa , which have been shown to catalyze translesion DNA synthesis past several DNA lesions. Steady-state kinetic analyses and analysis of translesion products have revealed that the synthesis is >100-fold more efficient with pol eta  than with pol kappa  and that both error-free and error-prone syntheses are observed with these enzymes. The miscoding events include both base substitution and frameshift mutations. These results suggest that both polymerases, particularly pol eta , may contribute to the translesion DNA synthesis events observed for 1,N6-ethenodeoxyadenosine in human cells.


    INTRODUCTION
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

In the last few years, several new human DNA polymerases (pols),1 which are likely to be involved in translesion DNA synthesis (TLS), were discovered. This list includes pol eta  (1), pol kappa  (2, 3), pol iota  (4), and pol zeta  (5). Pol eta , pol iota , and pol kappa  are encoded by the hRAD30A, hRAD30B, and DINB1 genes, respectively. These new pols form a Rad30/UmuC/DinB/REV1 superfamily (2, 3, 6). Pol zeta  consists of two gene products: hREV3 containing pol activity and hREV7 with an unknown function (5). In general, these pols catalyze TLS more efficiently than previously known pols. They synthesize DNA in a distributive manner and tend to show lower replication fidelity than other pols such as pol alpha , pol beta , and pol delta  when unmodified DNA is used as a template (7-10).

There are several pieces of evidence for the involvement of human pol eta  and pol zeta  in TLS in vivo (5, 11-13). Although the involvement of human pol kappa  or pol iota  has not yet been established in vivo, the Escherichia coli homologue of pol kappa , pol IV, has been shown to play a role in TLS in vivo (14). Pol eta , which is missing in xeroderma pigmentosum variant cells (13, 15), is shown to catalyze efficient TLS across the cis-syn cyclobutane thymine-thymine dimer by inserting two dAMPs opposite the lesion (16). Therefore, the cancer proneness of xeroderma pigmentosum variant patients is thought to be caused by the lack of accurate TLS across this and/or other UV photo products. Pol eta  also catalyzes TLS across other DNA lesions such as cisplatin G-G intrastrand cross-link (16), acetylaminofluorene-dG (16), and 8-oxodeoxyguanosine (17) with relatively high fidelity. On the other hand, TLS across (+)-trans-anti-benzo[a]pyrene-N2-dG is reported to be error-prone (18). Pol kappa  is also shown to conduct TLS across an abasic site (19, 20), acetylaminofluorene-dG (19, 20), (-)-trans-anti-benzo[a]pyrene-N2-dG (20), and 8-oxodeoxyguanosine (20).

Based on these findings, we are motivated to study the efficiency and fidelity of TLS catalyzed by these novel pols across 1,N6-ethenodeoxyadenosine (epsilon dA) to probe the in vivo TLS mechanism. We have shown that epsilon dA is miscoding in simian and human cells by inducing epsilon dAright-arrowT, epsilon dAright-arrowG, and epsilon dAright-arrowC (21, 22). This adduct is produced in animals exposed to vinyl compounds such as the human carcinogen vinyl chloride. Surprisingly, this adduct is also found in unexposed animals and humans with lipid peroxidation products being the suspected source of this adduct (23). Our in vitro primer extension studies indicate that pol eta  catalyzes TLS more efficiently than pol kappa  and that both pols catalyze error-free and error-prone TLS.

    MATERIALS AND METHODS
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ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

Materials-- [gamma -32P]ATP was purchased from Amersham Pharmacia Biotech. Human pol eta  and pol kappa  were purified as described (13, 19). Pol delta  was purified to apparent homogeneity from calf thymus (24). Human proliferating cell nuclear antigen (PCNA) was a generous gift from Paul Fisher (State University of New York, Stony Brook, NY). T4 polynucleotide kinase and EcoRI were purchased from New England Biolabs. Ultrapure deoxyribonucleic acid triphosphates were purchased from Roche Molecular Biochemicals.

DNA Substrates-- Oligonucleotides were purchased from Oligos Etc. (Wilsonville, OR) or synthesized in the laboratory of Francis Johnson (State University of New York, Stony Brook, NY). Oligomers were purified by electrophoresis on a 20% polyacrylamide gel containing 7 M urea, detected by UV shadowing, excised from the gel, eluted from gel slices, and desalted using a SEP-PAK C18 cartridge (Waters). Purified oligonucleotide primers were labeled at the 5' end with [gamma -32P]ATP and T4 polynucleotide kinase. Primers were annealed to templates by mixing at a 1:1.2 molar ratio in 10 mM Tris-HCl (pH 7.5), 1 mM EDTA, and 100 mM NaCl by heating to 80 °C followed by slow cooling. For primer extension and standing start kinetic studies (25) of nucleotide insertion and extension, the 32P-labeled primers (5'-GTTCTAGCGTGTAGGT, 5'-GTTCTAGCGTGTAGGTAT, and 5'-GTTCTAGCGTGTAGGTATN (where N = A, C, G, or T)) were annealed to a 28-mer template (5'-CTGCTCCTCXATACCTACACGCTAGAAC (where X = dA or epsilon dA)), generating substrates 1, 2, and 3, respectively.

To quantify various TLS products, the 38-mer template (5'-CATGCTGATGAATTCCTTCXCTACTTTCCTCTCCATTT (where X = dA or epsilon dA; EcoRI site shown in bold)) was annealed to the 32P-labeled primer (5'-AGAGGAAAGTAG), yielding substrate 4 (Fig. 2).

Primer Extension Assays-- Each reaction mixture (10 µl) contained 40 nM substrate 1 and 100 µM dNTPs. Reactions with pol eta  (1) or pol kappa  (19) contained 40 mM Tris-HCl (pH 8.0), 60 mM KCl, 5 mM MgCl2, 10 mM dithiothreitol (DTT), 2.5% glycerol, and 250 µg/ml bovine serum albumin (BSA). Reactions with pol delta  contained 7 ng/µl PCNA, 40 mM Bis-Tris (pH 6.8), 6 mM MgCl2, 2 mM DTT, 4% glycerol, and 40 µg/ml BSA. Pol eta  was diluted in 20 mM potassium phosphate (pH 7.5), 0.3 M KCl, 0.1 mM EDTA, 0.1 mg/ml BSA, 1 mM DTT, and 50% glycerol. Pol kappa  was diluted in 10 mM Tris-HCl (pH 7.4), 0.3 M KCl, 1 mM EDTA, 0.2 mg/ml BSA, 1 mM DTT, and 50% glycerol. Pol delta  was diluted in 40 mM Bis-Tris (pH 6.8), 1 mM DTT, 0.2 mg/ml BSA, and 10% glycerol. Reactions were initiated by adding enzyme and were incubated at 37 ± 1 °C for 10 min (pol eta  or pol kappa ) or 30 ± 1 °C for 30 min (pol delta ). Reactions were stopped by adding 10 µl of 95% formamide dye mixture (95% formamide, 10 mM EDTA, 0.001% xylene cyanol, and 0.001% bromphenol blue), and then the mixture was heated to 95 °C for 5 min. Aliquots (1 µl) were subjected to electrophoresis in a denaturing 20% polyacrylamide gel.

Kinetic Studies of Nucleotide Insertion and Extension-- Standing-start reactions (25) (10 µl) contained 40 nM substrate 2 or 3 (substrate 2 for insertion analysis and substrate 3 for extension analysis), 0-2 mM dNTP(s), and a reaction buffer (see above). Initiation and termination of reactions were conducted as described above. Aliquots (1 µl) were subjected to electrophoresis in a denaturing 20% polyacrylamide gel.

Data Analysis-- Integrated gel band intensities were measured using a PhosphorImager and ImageQuant software (Molecular Dynamics). Nucleotide incorporation parameters were determined (25). Less than 20% of the primers were extended in these steady-state kinetic analyses, ensuring single-hit kinetics (26). Values for the Michaelis-Menten constant (Km) and Vmax for incorporation opposite dA and epsilon dA were obtained by least squares nonlinear regression to a rectangular hyperbola. kcat was calculated by dividing Vmax by the enzyme concentration. The frequency of insertion (Fins) and extension (Fext) were calculated using the equation Fins or ext = (kcat/Km)adduct/(kcat/Km)control (25). Standard errors derived from the curve-fitting are included.

Analysis of TLS Products-- DNA synthesis reaction mixtures (10 µl) contained 50 nM substrate 4, 100 µM dNTPs, the appropriate buffer (see above), and enzyme (1.5 units of pol delta , 36 fmol of pol eta , or 56 fmol pol kappa ) were incubated at 23 ± 1 °C for 15 min and then 37 ± 1 °C for 45 min (27). Reactions were stopped by adding 10 µl of a formamide dye mixture and heating to 95 °C for 5 min. Samples were subjected to electrophoresis in a denaturing 20% polyacrylamide gel (35 × 42 × 0.04 cm). Full-length products were extracted from the gel and annealed to a complementary 38-mer. The annealed products were digested with EcoRI (100 units) for 1 h at 30 °C and then 1 h at 15 °C. This digestion generates 32P-labeled 18-mers from the fully extended products. The products were separated in a two-phase polyacrylamide gel (15 × 72 × 0.04 cm) (27). This method allows the separation of four base substitution products and frameshift products.

The DNA template of substrate 4 is different from the template of substrates 1, 2, and 3 in the DNA sequence surrounding epsilon dA. The sequence context used in the template of substrates 1, 2, and 3 is identical to that used in miscoding studies in human cells (22). It was not possible to separate various TLS products by the method described above when this sequence context was employed. Therefore, we used the sequence (substrate 4) that has been shown to permit separation of various TLS products by gel electrophoresis (27).

    RESULTS
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ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

DNA Polymerase Activity on Control and epsilon dA-Modified Templates-- Pol eta , pol kappa , and pol delta /PCNA were assayed for polymerase activity on both unmodified and epsilon dA-modified templates. The primer (substrate 1; Fig. 1A) allowed the addition of two nucleotides before encountering the adduct. Although all three pols were capable of synthesizing across epsilon dA (Fig. 1, B and C), this lesion posed a much stronger block to pol delta  than to pol eta  and pol kappa  when compared with the control templates. A very small amount of the full-length product was generated by pol delta  only when PCNA was added to the reaction mixture (compare lanes 10 and 11 with lane 12 in Fig. 1B), revealing the enhancing role for PCNA in TLS. Pol eta  seems to catalyze TLS more efficiently than pol kappa .


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Fig. 1.   Translesion DNA synthesis catalyzed by DNA polymerases. A, template-primer (substrate 1) used in B and C. B, calf thymus pol delta  (0 (lanes 1 and 7), 0.09 (lanes 2 and 8), 0.19 (lanes 3 and 9), 0.38 (lanes 4 and 10), and 0.75 units (lanes 5, 6, 11, and 12)) was incubated with substrate 1 (where X = dA in lanes 1-6 and X = epsilon dA in lanes 7-12) containing 5'-32P-labeled primer in a 10-µl reaction mixture at 30 °C for 30 min. Lanes 1-5 and 7-11 contained 70 ng of human PCNA. C, human pol eta  (0 (lanes 1 and 6), 0.29 (lanes 2 and 7), 1.5 (lanes 3 and 8), 7.3 (lanes 4 and 9), and 36.3 fmol (lanes 5 and 10)) or pol kappa  (0 (lanes 11 and 16), 0.25 (lanes 12 and 17), 1.2 (lanes 13 and 18), 6.2 (lanes 14 and 19), and 31 fmol (lanes 15 and 20)) was incubated with the substrate 1 (where X = dA in lanes 1-5 and 11-15 and X = epsilon dA in lanes 6-10 and 16-20) containing 5'-32P-labeled primer in a 10-µl reaction mixture at 37 °C for 10 min.

Kinetic Studies of Nucleotide Incorporation and Extension-- To determine the efficiency and fidelity of TLS catalyzed by pol eta  and pol kappa , we first determined steady-state kinetic parameters (Km and kcat) for nucleotide incorporation opposite dA and epsilon dA using substrate 2. The internal 13 nucleotides (5'-CTCCTCXATACCT) of this template are identical to those used in the miscoding studies in human cells (22). The kinetic data (Fins) indicate that pol eta  incorporates a nucleotide opposite epsilon dA more efficiently than pol kappa . Pol eta  inserts the correct dTMP opposite epsilon dA twice as efficiently as dAMP and dGMP and 13 times more efficiently than dCMP. This dTMP insertion is ~68 times less efficient than that opposite dA. Similarly, pol kappa  also inserts dTMP most efficiently opposite epsilon dA, followed by dGMP and then dAMP, but its efficiency is ~1000 times less than the incorporation opposite dA. These results indicate that dTMP, the correct nucleotide, is preferentially inserted opposite epsilon dA by both pols.

We then determined steady-state kinetic parameters for nucleotide extension from four different 3' termini located opposite dA or epsilon dA using substrate 3. The kinetic data (Fext) indicate that pol eta  extends from all the termini more efficiently than pol kappa . Pol eta  extends the primer with the correct dTMP terminus more efficiently than the other three termini when the modified template was used. This extension from the dTMP terminus is ~55 times less efficient than that from the dTMP terminus located opposite dA. In experiments using pol kappa , the efficiency of extension from the 3' terminus followed the order of dAMP > dGMP > dTMP > dCMP, indicating that unlike pol eta , the incorrect pairings are extended better than the correct epsilon dA:T pairing.

Based on these insertion and extension kinetic parameters, the relative efficiency of TLS was determined by multiplying Fins and Fext. The results indicate that pol eta  catalyzes TLS across epsilon dA more efficiently than pol kappa . With pol eta , TLS with epsilon dA:T is dominant, and its efficiency is 3.0, 4.4, and 45 times greater than TLS with epsilon dA:A, epsilon dA:G, and epsilon dA:C, respectively. The same analysis for pol kappa  shows that the efficiency of TLS with epsilon dA:T is 2.1 and 2.7 times greater than TLS with epsilon dA:A and epsilon dA:G, respectively. These results indicate that accurate TLS is dominant but not exclusive with both pols.

Miscoding Specificity of epsilon dA-- Because steady-state kinetic analysis includes only one of four dNTPs in the reaction mixture, and frameshift mutations are not detected, we determined the miscoding specificity of epsilon dA in the presence of four dNTPs. We analyzed polymerization products using substrate 4 (Fig. 2). Although fully extended products were observed with the unmodified template for all three pols, only pol eta  and pol kappa  produced full-length products with the modified template (data not shown). One possible explanation is that the 10-mer primer is not long enough to accommodate both pol delta  and PCNA (28), and pol delta  alone cannot catalyze TLS as shown in Fig. 1B.


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Fig. 2.   Miscoding specificity of epsilon dA in reactions catalyzed by pol delta , pol eta , or pol kappa . The annealed primer-template complex (substrate 4) is shown on top (where X = dA or epsilon dA). Aliquots of the reaction mixtures were subjected to two-phase 20% polyacrylamide gel electrophoresis. The mobilities of the reaction products were compared with those of standard 18-mers (lanes 1 and 7) containing dA, dC, dG, or dT opposite the lesion and with those of standards containing one- (Delta 1) and two-base (Delta 2) deletions.

Fully extended products were digested with EcoRI and electrophoresed in a two-phase polyacrylamide gel. When the unmodified template was used, pol delta -catalyzed products showed only one band (Fig. 2, lane 2) that co-migrated with the dT marker, indicating accurate DNA synthesis. Pol kappa  also catalyzed faithful synthesis (Fig. 2, lane 5). Pol eta  mainly catalyzed error-free DNA synthesis, but two additional bands were also observed, co-migrating with the dG and two-base deletion standards (Fig. 2, lane 3), indicating that pol eta  produced errors on the unmodified template. When the modified template was used, at least five and four products were observed for pol eta  and pol kappa , respectively (Fig. 2, lanes 4 and 6), co-migrating with the dG, dA, dT, dC, or one-base deletion markers (Fig. 2, lanes 1 and 7). These products were quantified based on the amount of radioactivity in the bands (Table II). Consistent with the results of the steady-state kinetic analysis, pol eta  dominantly catalyzed accurate TLS with dT on the modified template. However, substantial amounts of products containing dA, dG, dC, or one-base deletion were also observed. On the other hand, pol kappa  dominantly catalyzed TLS with one-base deletion, followed by dT, dA, and dC incorporation. The results shown in Table II indicate that error-prone TLS is dominant for both pols when frameshift mutations are included and that pol eta  catalyzes accurate TLS more frequently than pol kappa , but still more than 50% of the TLS is error-prone.

    DISCUSSION
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ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

Pol eta  has been reported to catalyze TLS across several DNA lesions in a relatively error-free manner (1, 16, 17). Our steady-state kinetic analyses and the analysis of TLS products have revealed that TLS catalyzed by pol eta  across epsilon dA, like the benzo[a]pyrene dG adduct (18), is significantly erroneous. Although accurate TLS with dTMP insertion opposite epsilon dA is predominant, pol eta  also frequently catalyzed erroneous TLS, causing base substitutions and frameshift mutations (Tables I and II and Fig. 2). Pol kappa  catalyzes TLS across several DNA lesions in relatively error-free and error-prone manners (19, 20). Our steady-state kinetic analysis shows that pol kappa  preferentially incorporates dTMP, followed by dAMP, opposite epsilon dA (Table I). The product analysis experiment (Table II and Fig. 2), however, has revealed that one-base deletion events were dominant followed by dTMP insertion products, indicating that pol kappa -catalyzed TLS is also erroneous. Neither pol eta  nor pol kappa  can be characterized as simply error-free or error-prone polymerases.

                              
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Table I
Kinetic parameters for nucleotide insertion and chain extension catalyzed by pol eta  and pol kappa  
ND, not determined.

                              
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Table II
Miscoding properties of varepsilon dA in reactions catalyzed by pol delta , pol eta , or pol kappa  
Numbers represent amounts of products expressed as a percentage of a total amount of fully extended products. Delta 1, one-base deletion; Delta 2, two-base deletion.

The overall efficiency of TLS, determined by Finc × Fext, for A:epsilon dA and G:epsilon dA is similar for both pols: 9.0 × 10-5 versus 6.1 × 10-5 for pol eta  and 1.5 × 10-5 versus 1.2 × 10-5 for pol kappa  (Table I). However, analysis of TLS products shows that dA incorporation is preferred to dG by both pols: 19.8% dA versus 9.1% dG for pol eta  and 18.8% dA versus 2.9% dG for pol kappa  (Table II). It is likely that some dGMP incorporated opposite epsilon dA misaligned (Fig. 3, step 3) to generate a one-base deletion, whereas dAMP incorporation does not cause this misalignment. Accordingly, dAMP incorporation opposite epsilon dA leads to a base substitution, whereas dGMP incorporation results in both a base substitution and a one-base deletion. Another mechanism envisioned is "dNTP-stabilized misalignment," which was observed for pol beta  in TLS across abasic sites (29). According to this mechanism, the slippage event occurs first, causing epsilon dA to be extrahelical (step 2), and the incoming dGTP stabilizes this misalignment (step 4). Continuous extension from this terminus results in a one-base deletion (step 5), whereas realignment (step 7) and extension (step 8) result in a base substitution. The hallmark of the dNTP-stabilized misalignment mechanism is the relatively low Km for dNMP insertion at the terminus opposite a DNA lesion, which suggests that the incorporation is actually opposite the base 5' to the lesion (29). In the insertion kinetic studies with pol eta , the Km value for dGMP insertion opposite epsilon dA (42.7 µM) is not much different from that for dTMP insertion opposite dA (21.4 µM) (Table I), which suggests that dGMP is inserted opposite dC, 5' to epsilon dA, and extension from this terminus results in a one-base deletion (steps 2 to 4 to 5). On the other hand, with pol kappa  the Km value for dGMP insertion opposite epsilon dA (126 µM) is very different from that for dTMP insertion opposite dA (9.4 µM) (Table I). This suggests that dGMP is incorporated opposite epsilon dA, followed by misalignment and subsequent extension of the primer. This is the likely mechanism for the induction of one-base deletions (the dominant event) by pol kappa .


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Fig. 3.   Model for the induction of base substitutions and one-base deletions after the incorporation of dGMP. dGMP is inserted opposite epsilon dA (X) (step1). This terminal dG is extended (step 6) or misaligned with dC located 5' to X, rendering X extrahelical (step3). Extension of the misaligned primer generates one-base deletion (step 5). Realignment (step 7) and extension (step 8) yields a base substitution mutation. Misalignment is also generated by the dNTP-stabilized misalignment mechanism (29) in which a slippage event occurs first, causing X to be extrahelical (step 2), and the incoming dGTP stabilizes this misalignment (step 4).

Our mutagenesis experiments (22) have shown that miscoding events account for 10-20% of TLS in human cells. Although it is not possible to speculate as to what extent these pols contribute to TLS in vivo, our results suggest that if these pols are involved in TLS in vivo, then it is likely to be error-prone. In vivo experiments using human cells lacking these pols are necessary to clarify this point.

    ACKNOWLEDGEMENTS

We thank F. Johnson, C. Torres, and S. Shibutani for oligonucleotides used in this research.

    FOOTNOTES

* This work was supported by United States Public Health Service Grant CA76163 (to M. M.), the Pharmaceutical Research and Manufacturers of America Foundation (to R. L. L.), and grants from Core Research for Evolution Science and Technology, Japan Science and Technology Corporation (to F. H.) and the Bioarchitect Research Project of the Institute of Physical and Chemical Research (to F. H.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

|| To whom correspondence should be addressed: Tel.: 631-444-3082; Fax: 631-444-7641; E-mail: maki@pharm.sunysb.edu.

Published, JBC Papers in Press, March 16, 2001, DOI 10.1074/jbc.M102158200

    ABBREVIATIONS

The abbreviations used are: pol, DNA polymerase; TLS, translesion DNA synthesis; epsilon dA, 1,N6-ethenodeoxyadenosine; PCNA, proliferating cell nuclear antigen; DTT, dithiothreitol; BSA, bovine serum albumin.

    REFERENCES
TOP
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES

1. Masutani, C., Araki, M., Yamada, A., Kusumoto, R., Nogimori, T., Maekawa, T., Iwai, S., and Hanaoka, F. (1999) EMBO J. 18, 3491-3501[Abstract/Free Full Text]
2. Ogi, T., Kato, T., Jr., Kato, T., and Ohmori, H. (1999) Genes Cells 4, 607-618[Abstract/Free Full Text]
3. Gerlach, V. L., Aravind, L., Gotway, G., Schultz, R. A., Koonin, E. V., and Friedberg, E. C. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 11922-11927[Abstract/Free Full Text]
4. McDonald, J. P., Rapic-Otrin, V., Epstein, J. A., Broughton, B. C., Wang, X., Lehmann, A. R., Wolgemuth, D. J., and Woodgate, R. (1999) Genomics 60, 20-30[CrossRef][Medline] [Order article via Infotrieve]
5. Gibbs, P. E., McGregor, W. G., Maher, V. M., Nisson, P., and Lawrence, C. W. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 6876-6880[Abstract/Free Full Text]
6. Johnson, R. E., Washington, M. T., Prakash, S., and Prakash, L. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 12224-12226[Free Full Text]
7. Johnson, R. E., Washington, M. T., Prakash, S., and Prakash, L. (2000) J. Biol. Chem. 275, 7447-7450[Abstract/Free Full Text]
8. Matsuda, T., Bebenek, K., Masutani, C., Hanaoka, F., and Kunkel, T. A. (2000) Nature 404, 1011-1013[CrossRef][Medline] [Order article via Infotrieve]
9. Ohashi, E., Bebenek, K., Matsuda, T., Feaver, W. J., Gerlach, V. L., Friedberg, E. C., Ohmori, H., and Kunkel, T. A. (2000) J. Biol. Chem. 275, 39678-39684[Abstract/Free Full Text]
10. Tissier, A., McDonald, J. P., Frank, E. G., and Woodgate, R. (2000) Genes Dev. 14, 1642-1650[Abstract/Free Full Text]
11. Lehmann, A. R., Kirk-Bell, S., Arlett, C. F., Paterson, M. C., Lohman, P. H., de Weerd-Kastelein, E. A., and Bootsma, D. (1975) Proc. Natl. Acad. Sci. U. S. A. 72, 219-223[Abstract]
12. Wang, Y. C., Maher, V. M., and McCormick, J. J. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 7810-7814[Abstract]
13. Masutani, C., Kusumoto, R., Yamada, A., Dohmae, N., Yokoi, M., Yuasa, M., Araki, M., Iwai, S., Takio, K., and Hanaoka, F. (1999) Nature 399, 700-704[CrossRef][Medline] [Order article via Infotrieve]
14. Napolitano, R., Janel-Bintz, R., Wagner, J., and Fuchs, R. P. (2000) EMBO J. 19, 6259-6265[Abstract/Free Full Text]
15. Johnson, R. E., Kondratick, C. M., Prakash, S., and Prakash, L. (1999) Science 285, 263-265[Abstract/Free Full Text]
16. Masutani, C., Kusumoto, R., Iwai, S., and Hanaoka, F. (2000) EMBO J. 19, 3100-3109[Abstract/Free Full Text]
17. Haracska, L., Yu, S. L., Johnson, R. E., Prakash, L., and Prakash, S. (2000) Nat. Genet. 25, 458-461[CrossRef][Medline] [Order article via Infotrieve]
18. Zhang, Y., Yuan, F., Wu, X., Rechkoblit, O., Taylor, J. S., Geacintov, N. E., and Wang, Z. (2000) Nucleic Acids Res. 28, 4717-4724[Abstract/Free Full Text]
19. Ohashi, E., Ogi, T., Kusumoto, R., Iwai, S., Masutani, C., Hanaoka, F., and Ohmori, H. (2000) Genes Dev. 14, 1589-1594[Abstract/Free Full Text]
20. Zhang, Y., Yuan, F., Wu, X., Wang, M., Rechkoblit, O., Taylor, J. S., Geacintov, N. E., and Wang, Z. (2000) Nucleic Acids Res. 28, 4138-4146[Abstract/Free Full Text]
21. Pandya, G. A., and Moriya, M. (1996) Biochemistry 35, 11487-11492[CrossRef][Medline] [Order article via Infotrieve]
22. Levine, R. L., Yang, I. Y., Hossain, M., Pandya, G. A., Grollman, A. P., and Moriya, M. (2000) Cancer Res. 60, 4098-4104[Abstract/Free Full Text]
23. Singer, B., and Bartsch, H. (1999) Exocyclic DNA Adducts in Mutagenesis and Carcinogenesis , p. 150, International Agency for Research on Cancer, Lyon, France
24. Ng, L., Tan, C. K., Downey, K. M., and Fisher, P. A. (1991) J. Biol. Chem. 266, 11699-11704[Abstract/Free Full Text]
25. Creighton, S., Bloom, L. B., and Goodman, M. F. (1995) Methods Enzymol. 262, 232-256[Medline] [Order article via Infotrieve]
26. Goodman, M. F., Creighton, S., Bloom, L. B., and Petruska, J. (1993) Crit. Rev. Biochem. Mol. Biol. 28, 83-126[Abstract]
27. Shibutani, S., Suzuki, N., Matsumoto, Y., and Grollman, A. P. (1996) Biochemistry 35, 14992-14998[CrossRef][Medline] [Order article via Infotrieve]
28. Mozzherin, D. J., Tan, C. K., Downey, K. M., and Fisher, P. A. (1999) J. Biol. Chem. 274, 19862-19867[Abstract/Free Full Text]
29. Efrati, E., Tocco, G., Eritja, R., Wilson, S. H., and Goodman, M. F. (1997) J. Biol. Chem. 272, 2559-2569[Abstract/Free Full Text]


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