The High Mobility Group Domain Protein Cmb1 of Schizosaccharomyces pombe Binds to Cytosines in Base Mismatches and Opposite Chemically Altered Guanines

The mismatch-binding activity Cmb1 of Schizosaccharomyces pombe was enriched from wild type cells, and N-terminal sequencing enabled cloning of the respective gene. The deduced amino acid sequence of cmb1 +contains a high mobility group domain, a motif that is common to a heterogeneous family of DNA-binding proteins. In crude protein extracts of a cmb1 gene-disruption strain, specific binding to C/T, C/A, and C/Δ was abolished. Weak binding to C/C revealed the presence of a second mismatch-binding activity, Cmb2. Cmb1, enriched fromS. pombe and purified from Escherichia coli,bound specifically to C/C, C/T, C/A, T/T, and C/Δ but showed little or no affinity to other mismatches and small loops. Cmb1 recognizes 1,2 GpG intrastrand cross-links, produced by the chemotherapeutic drug cisplatin, when two cytosines are opposite the cross-linked guanines but not when other bases are present. Consistently, O6-methylguanine:C but not O6-methylguanine/T lesions were bound. Thus, cytosines in mismatches and opposite chemically modified guanines are the preferred target of Cmb1 recognition. cmb1 mutant cells are more sensitive to cisplatin than wild type cells, indicating a role of Cmb1 in repair of cisplatin-induced DNA damage. The mismatch-binding activity Cmb1 of Schizosaccharomyces pombe was enriched from wild type cells, and N-terminal sequencing enabled cloning of the respective gene. The deduced amino acid sequence of cmb1 +contains a high mobility group domain, a motif that is common to a heterogeneous family of DNA-binding proteins. In crude protein extracts of a cmb1 gene-disruption strain, specific binding to C/T, C/A, and C/Δ was abolished. Weak binding to C/C revealed the presence of a second mismatch-binding activity, Cmb2. Cmb1, enriched fromS. pombe and purified from Escherichia coli,bound specifically to C/C, C/T, C/A, T/T, and C/Δ but showed little or no affinity to other mismatches and small loops. Cmb1 recognizes 1,2 GpG intrastrand cross-links, produced by the chemotherapeutic drug cisplatin, when two cytosines are opposite the cross-linked guanines but not when other bases are present. Consistently, O6-methylguanine:C but not O6-methylguanine/T lesions were bound. Thus, cytosines in mismatches and opposite chemically modified guanines are the preferred target of Cmb1 recognition. cmb1 mutant cells are more sensitive to cisplatin than wild type cells, indicating a role of Cmb1 in repair of cisplatin-induced DNA damage. nucleotide excision repair cis-diamine-dichloroplatinum(II) O6-methylguanine N-methyl-N′-nitro-N-nitrosoguanidine O4-methylthymine high mobility group trans-diamine-dichloroplatinum (II) polymerase chain reaction base pair(s) kilobase pair(s) open reading frame cytosine mismatch binding. DNA can be damaged by a variety of physical and chemical agents. Most types of lesions are efficiently removed from DNA by repair mechanisms. The nucleotide excision repair (NER)1 system is able to correct a broad spectrum of adducts, including cyclobutane pyrimidine dimers and 6-4 photoproducts caused by ultraviolet light, intrastrand cross-links formed by cis-diamine-dichloroplatinum(II) (cisplatin), as well as O6-methylguanine (O6meG) produced by methylating agents such asN-methyl-N′-nitro-N-nitrosoguanidine (MNNG) (1Huang J.-C. Hsu D.S. Kazantsev A. Sancar A. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 12213-12217Crossref PubMed Scopus (211) Google Scholar, 2Friedberg E.C. Walker G.C. Siede W. DNA Repair and Mutagenesis. American Society for Microbiology, Washington, D. C.1995: 191-365Google Scholar, 3Sancar A. Annu. Rev. Biochem. 1996; 65: 43-81Crossref PubMed Scopus (960) Google Scholar). The mutHLS-like mismatch-repair pathway efficiently corrects most base-base mismatches and small DNA loops, which frequently occur during replication by misincorporation of bases and strand slippage, respectively (4Modrich P. Lahue R. Annu. Rev. Biochem. 1996; 65: 101-133Crossref PubMed Scopus (1322) Google Scholar, 5Kolodner R.D. Genes Dev. 1996; 10: 1433-1442Crossref PubMed Scopus (540) Google Scholar). A defect in the human geneshMSH2 (a homologue of Escherichia coli MutS),hMLH1, hPMS1, or hPMS2 (all of which are MutL homologues) is responsible for the heritable cancer syndrome hereditary nonpolyposis colon cancer. The clinical symptoms of patients with homozygously mutated hMSH2, hMLH1, orhPMS2 genes are accompanied by microsatellite instability and mismatch repair deficiency, whereas there is no indication thathPMS1 has a role in mismatch repair (4Modrich P. Lahue R. Annu. Rev. Biochem. 1996; 65: 101-133Crossref PubMed Scopus (1322) Google Scholar, 6Jiricny J. Trends Genet. 1994; 10: 164-168Abstract Full Text PDF PubMed Scopus (75) Google Scholar, 7Kolodner R.D. Trends Biochem. Sci. 1995; 20: 397-401Abstract Full Text PDF PubMed Scopus (278) Google Scholar). The human mismatch-binding activity hMutSα, a heterodimer of the two MutS homologous proteins hMSH2 and GTBP (8Drummond J.T. Li G.M. Longley M.J. Modrich P. Science. 1995; 268: 1909-1912Crossref PubMed Scopus (534) Google Scholar, 9Palombo F. Gallinari P. Iaccarino I. Lettieri T. Hughes M. D'Arrigo A. Truong O. Hsuan J.J. Jiricny J. Science. 1995; 268: 1912-1914Crossref PubMed Scopus (476) Google Scholar), also recognizes DNA lesions containing O6meG, O4-methylthymine, and cisplatin-induced 1,2 GpG intrastrand cross-links (10Duckett D.R. Drummond J.T. Murchie A.I. Reardon J.T. Sancar A. Lilley D.M.J. Modrich P. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 6443-6447Crossref PubMed Scopus (372) Google Scholar). Thus, mismatch-repair proteins and NER proteins might compete in repair of some types of DNA lesions. Whereas repair mediated by the NER system normally restores wild type information, the action of mismatch-repair proteins on lesions rather contribute to cytotoxicity (11Branch P. Aquilina G. Bignami M. Karran P. Nature. 1993; 362: 652-654Crossref PubMed Scopus (349) Google Scholar, 12Umar A. Kunkel T.A. Eur. J. Biochem. 1996; 238: 297-307Crossref PubMed Scopus (201) Google Scholar). Several high mobility group (HMG) proteins are known to bind to GpG intrastrand cross-links (13Zamble D.B. Lippard S.J. Trends Biochem. Sci. 1995; 20: 435-439Abstract Full Text PDF PubMed Scopus (478) Google Scholar). Binding by HMG-1 shields the lesion from excision by the human excinuclease protein complex (14Huang J.-C. Zamble D.B. Reardon J.T. Lippard S.J. Sancar A. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 10394-10398Crossref PubMed Scopus (341) Google Scholar). Consistently, aSaccharomyces cerevisiae mutant, defective in the HMG-box gene IXR1, is more resistant to cisplatin than wild type (15Brown S.J. Kellet P.J. Lippard S.J. Science. 1993; 261: 603-605Crossref PubMed Scopus (180) Google Scholar). We have identified a mismatch-binding activity in Schizosaccharomyces pombe crude extracts showing high affinity to cytosine-containing mismatches (16Fleck O. Schär P. Kohli J. Nucleic Acids Res. 1994; 22: 5289-5295Crossref PubMed Scopus (13) Google Scholar). Here, we describe the purification of this activity, Cmb1, and cloning of the respective gene. DNA sequencing revealed that Cmb1 contains a HMG domain. Cmb1 was purified from an E. coli overexpression strain and tested for binding to mismatches, small DNA loops, and substrates containing either GpG intrastrand cross-links or O6meG. Furthermore, we addressed the question of whether a cmb1 mutant responds differently to the chemicals cisplatin, transplatin, and MNNG. Binding of Cmb1 protein to DNA substrates was tested with a band shift assay. Substrates and competitor DNA used to test binding to mismatches, loops, and O6meG lesions are in the M13mp9 polylinker sequence context (16Fleck O. Schär P. Kohli J. Nucleic Acids Res. 1994; 22: 5289-5295Crossref PubMed Scopus (13) Google Scholar). The sequence of the platinated substrates and their unplatinated controls is shown in Fig. 6 A. For platination, 1 pmol of plus strand was incubated for 24 h at 37 °C in 100 μl of 10 mm Tris-HCl (pH 7.5) containing either 0.1 mmcisplatin or 0.1 mm transplatin (Sigma). Unreacted cisplatin or transplatin was removed by chromatography on Sephadex G25 (Amersham Pharmacia Biotech). The extent of platinated oligonucleotides was checked on a 6% polyacrylamide gel and was estimated to be approximately 60–80%. Modified and unmodified strands were 5′-end-labeled by T4 polynucleotide kinase (Promega) in the presence of [γ-32P]ATP and annealed with their complementary strands as described (16Fleck O. Schär P. Kohli J. Nucleic Acids Res. 1994; 22: 5289-5295Crossref PubMed Scopus (13) Google Scholar). To test binding to the various substrates, 20-μl reactions were performed for 15 min at 4 °C in 25 mm Tris-HCl (pH 7.5), 0.5 mm dithiothreitol, 4 mm spermidine, 0.5 mm EDTA, 10% glycerol, 0.01 mm ZnCl2, 50–200 mm NaCl in the presence of 40 fmol radiolabeled substrate. The amount of unlabeled homoduplex DNA as competitor and the source of protein are in the were by 4 in 6% polyacrylamide in 40 mm Tris-HCl (pH 7.5), mm 1 mm were to The for S. pombe cells for protein extracts was as described (16Fleck O. Schär P. Kohli J. Nucleic Acids Res. 1994; 22: 5289-5295Crossref PubMed Scopus (13) Google Scholar), that we used A mm Tris-HCl (pH at mm 1 mm EDTA, 0.5 0.1 mm 0.1 mm 1 mm for and To the of of Cmb1, protein from purification were on by and with or For protein were at 4 of cells in and at were A for a with of mm in was used for of with at min of on The were and for 1 h at in a The was from and was to a of and the was by min of at in mm Tris-HCl (pH at mm 0.1 mm EDTA, 10% mm 0.1 mm and of The was at a of on two with The of was at a of on a with proteins were by a from to as that and and were and 4 of to of was at a of on a with proteins were with of and respectively from in NaCl of and The mismatch-binding activity Cmb1 at A was for N-terminal sequencing The of the were of of and on a 1 Pharmacia at a of 0.5 proteins were by of by a from to 1 Cmb1 at NaCl of the but was also in the and in the by indicating that the was the of this enabled the of the mismatch binding activity as a protein were mm Tris-HCl (pH 7.5), mm 0.1 mm EDTA, mm and at °C For N-terminal a of was to μl by min of at in two were on a to an by and with and the protein band was The N-terminal sequence of amino was by and of a were performed in a DNA reactions of μl pmol of of two 0.1 mm 1 of DNA polymerase in a either of S. pombe DNA or 10 of DNA for the of gene and for cloning of cmb1 the E. coli were min at by of of at 1 min of at a on the of the are for and 1 min of at a at °C was from this are in the The amino acid sequence from the Cmb1 protein was used to a of gene from S. from the and or from a of this sequence were used for from the amino acid sequence from and from and and bases at their A of the was with but not with was performed by with an of 40 by with an of were on A band of the was from the gel W. M.J. Biochem. 1995; PubMed Scopus Google and used for with and and for with and reaction at produced a indicating that the the sequence of The DNA was and was used for The was with to DNA Pharmacia and used to a of S. pombe PubMed Scopus Google by this with a open reading frame of cmb1 were A containing of the was by with and at The was radiolabeled with and to and E. R. D. F. 1993; Full Text PDF PubMed Scopus Google Scholar, E. R. Genet. PubMed Scopus Google Scholar). and were which on and E. R. D. F. 1993; Full Text PDF PubMed Scopus Google Scholar). from the of were in to to was by the a sequencing The cmb1 was from strands with from and with from the were with the The in of the of cmb1 by A of the and a of the of cmb1 were by at with DNA polymerase For the and were and for the and were The at their for cloning were to the and of the in A containing was a S. pombe h strain Genet. 1994; PubMed Scopus Google Scholar). were checked by for correct gene not was for The cmb1 gene was by at polymerase and from the and of the A the nucleotide sequence for the amino was with and at and a and contains a The were with and with The were E. coli strain and containing correct were checked for by For of the the were coli strain of the were in containing 100 and incubated at 37 °C of was was to a of 1 h of cells were by 10 min of at in A. in cells were at °C To crude protein extracts containing Cmb1 or was to the cells of the were by on for with at 1 min on min of at the was removed protein The strain containing with the gene was used for purification of the respective of protein in was from a E. coli and at a of on a with proteins were by of by a from to mm at The were and in to of protein in was at a of on a proteins were with 10 of containing mm by a from to mm and mm and at this a of other proteins were in but not in the other containing an purification was with were and the NaCl was to mm by of as but The of protein in was at a of on a with a from to mm NaCl was at other proteins be in a was and in at °C of protein in To test of S. pombe cells to various 1 cells from were incubated with in of and and of cisplatin transplatin or were incubated with either cisplatin or transplatin for min or with for The cells were with of and in were on and with and were incubated for at °C The were in the of cisplatin, two with transplatin, and with MNNG. activity binding to cytosine-containing mismatches was identified in S. pombe crude extracts (16Fleck O. Schär P. Kohli J. Nucleic Acids Res. 1994; 22: 5289-5295Crossref PubMed Scopus (13) Google Scholar). We enriched this activity, Cmb1, from extracts of an S. pombe wild type strain by by chromatography and of the from the purification by a revealed a of the activity in and 1 The of the band shift well with the of a band in a gel by 1 The also a second protein of and a other proteins at were tested for their mismatch-binding We affinity to C/A, and C/Δ and some binding to C/C and or binding was to homoduplex and to substrates with a or mismatch 1 pmol of the Cmb1 protein were used for N-terminal sequencing and in the of amino from the sequence of Cmb1 were used for A band of the with was from the gel and to with A band was indicating that the the sequence of of the from revealed with the for the amino acid sequence from the Cmb1 The of was used to a S. pombe PubMed Scopus Google Scholar). Several were but of the open reading frame of cmb1 at of the and of the sequence from the A of this was used as for and E. R. D. F. 1993; Full Text PDF PubMed Scopus Google Scholar, E. R. Genet. PubMed Scopus Google Scholar). and were that on and E. R. D. F. 1993; Full Text PDF PubMed Scopus Google Scholar). from the of were in sequencing the of cmb1 gene E. F. Eur. J. Biochem. PubMed Scopus Google was to be approximately from the of cmb1 which is with the of cmb1 and sequencing of cmb1 revealed an of a The purified Cmb1 has a of from N-terminal amino acid sequence used for a the N-terminal amino in the of cmb1 base with the deduced amino acid sequence of cmb1 a HMG was identified in the DNA-binding motif is common to a family of HMG proteins in various (13Zamble D.B. Lippard S.J. Trends Biochem. Sci. 1995; 20: 435-439Abstract Full Text PDF PubMed Scopus (478) Google Scholar, R. J. Trends Genet. 1994; 10: Full Text PDF PubMed Scopus Google Scholar). HMG-1 and were to be of with high mobility in The HMG Scholar). A of proteins were identified that to of to of HMG-1 and R. J. Trends Genet. 1994; 10: Full Text PDF PubMed Scopus Google Scholar, A. R. Nature. PubMed Scopus Google Scholar). were HMG HMG proteins are that specific DNA whereas some are known to bind to specific DNA such as M. G. Science. PubMed Scopus Google Scholar, 1994; PubMed Scopus Google Scholar), intrastrand cross-links (13Zamble D.B. Lippard S.J. Trends Biochem. Sci. 1995; 20: 435-439Abstract Full Text PDF PubMed Scopus (478) Google Scholar, S.J. Kellet P.J. Lippard S.J. Science. 1993; 261: 603-605Crossref PubMed Scopus (180) Google or of M. S. PubMed Scopus Google Scholar). base revealed that also hPMS1, a human MutL R.D. G.M. A. Nature. 1994; PubMed Scopus Google Scholar), contains a HMG domain. A of the HMG of Cmb1 revealed that is a common to other HMG M. S. PubMed Scopus Google Scholar, G. Nucleic Acids Res. PubMed Scopus Google Scholar). A amino are HMG whereas are in proteins R. J. Trends Genet. 1994; 10: Full Text PDF PubMed Scopus Google Scholar). In this Cmb1 to the of HMG proteins The strain was as described the mutant is has no We tested mismatch binding with crude protein extracts from the In to extracts from wild in which binding to cytosine-containing was no binding to C/A, C/T, or C/Δ mismatches was with the mutant extracts binding to C/C a second activity for binding to C/C in S. not bind to other mismatches, whereas Cmb1 specifically to C/C, C/A, and 1 The cmb1 and a were in E. The a to the enriched from S. pombe extracts of overexpression were tested for mismatch binding. and extracts an activity that to the mismatches C/C, C/A, C/T, and but to other mismatches and to homoduplex not The complex was not when or a strain containing the were in gel and mismatch Cmb1, and the Cmb1 enriched from S. pombe were not overexpression of was than overexpression of the For binding the protein was purified was tested for binding to substrates containing base-base mismatches, and small with two or nucleotide A complex was formed when C/C or C/Δ mismatches were and Weak or no was with and substrates Thus, cytosine is well but not an or the other is not on the presence of or cytosines as two or cytosines in a were by and Several HMG proteins are known to bind to 1,2 GpG intrastrand cross-links (13Zamble D.B. Lippard S.J. Trends Biochem. Sci. 1995; 20: 435-439Abstract Full Text PDF PubMed Scopus (478) Google Scholar, S.J. Kellet P.J. Lippard S.J. Science. 1993; 261: 603-605Crossref PubMed Scopus (180) Google Scholar). We were to whether Cmb1 also specific binding to this type of lesion 6 either platinated or were substrates 6 1 and A complex was formed with unplatinated homoduplex which might a of Cmb1 for binding to the was binding was to opposite the 1,2 cross-linked other bases were of the cytosines the of cytosine complex Binding to the lesions with was as or to homoduplex and to a containing a mismatch in the sequence context affinity to lesion was not intrastrand is produced by transplatin, an of To the role of Cmb1 in repair of lesions produced by either cisplatin or transplatin, the cytotoxicity of was tested in wild type and the cmb1 The cmb1 strain was more sensitive to cisplatin than wild In the presence of was 6 the other when cells were with transplatin at 1 and no in was wild type and mutant not The action of is to of O6meG can with cytosine and a in DNA is frequently during replication to in of a T. M. Annu. Rev. Biochem. PubMed Scopus Google Scholar). We tested binding of Cmb1 to types of lesions. a cytosine was opposite the modified a complex was formed that was of to that with the containing a C/C mismatch and In binding to was as as to homoduplex DNA and to containing S. pombe cells, defective in were with of no from wild type cells was in We have described the of an activity in S. pombe crude extracts that efficiently to the cytosine-containing mismatches C/C, C/A, and C/Δ and to (16Fleck O. Schär P. Kohli J. Nucleic Acids Res. 1994; 22: 5289-5295Crossref PubMed Scopus (13) Google Scholar). We purification of the activity, Cmb1, from S. type cells and cloning of the gene. The of cmb1 a protein with amino indicating that a was enriched from S. we no in mismatch the Cmb1 and the when in E. The Cmb1 protein contains an HMG at the HMG proteins are known to specific DNA such as M. S. PubMed Scopus Google Scholar), DNA M. G. Science. PubMed Scopus Google Scholar, 1994; PubMed Scopus Google Scholar), and intrastrand cross-links (13Zamble D.B. Lippard S.J. Trends Biochem. Sci. 1995; 20: 435-439Abstract Full Text PDF PubMed Scopus (478) Google Scholar, S.J. Kellet P.J. Lippard S.J. Science. 1993; 261: 603-605Crossref PubMed Scopus (180) Google Scholar). a role in DNA and DNA also contains an HMG is of the human MutL a to the colon cancer syndrome hereditary nonpolyposis colon cancer R.D. Trends Biochem. Sci. 1995; 20: 397-401Abstract Full Text PDF PubMed Scopus (278) Google Scholar, R.D. G.M. A. Nature. 1994; PubMed Scopus Google Scholar). The purification of Cmb1 from S. pombe cells in which the Cmb1 protein but also a other proteins the of mismatch binding well with the of the Cmb1 protein in the various from the purification not be that mismatch binding was by protein in the to Cmb1 from the S. pombe proteins by not We to test binding with Cmb1 protein purified from E. In a the cmb1 as well as a which is the amino the purified from were in E. coli and tested for mismatch binding. in was the two Cmb1 and Cmb1 enriched from S. In the E. coli strain containing the the specific mismatch-binding complex was not is that Cmb1 is able to bind to mismatches the of pombe proteins. We purified from E. coli cells and tested binding to mismatches and small DNA loops. Cmb1 recognizes C/C, C/A, C/T, T/T, and a C/Δ but no or affinity to other types of mismatches and and not cytosine is by Cmb1, two or cytosines are substrates Thus, cytosine-containing base mismatches a DNA that is by a type of HMG binding is from E. coli MutS and which are able to bind to types of base mismatches P. Annu. Rev. Genet. PubMed Scopus Google Scholar, J.J. Lahue J. 1993; 268: Full Text PDF PubMed Google Scholar, E. 1996; PubMed Scopus Google Scholar, P. S. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar, I. F. Drummond J. Hsuan J.J. Modrich P. Jiricny J. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). The is most for C/C mismatches, which are a for binding and repair coli and MutS proteins. A human mismatch-binding activity was identified that to C/T, and mismatches of the MutS homologue hMSH2 P. P. Karran P. J. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). is to that of Cmb1 that C/C mismatches were by the human gene strain was tested for the presence of the mismatch-binding binding to C/A, C/T, and C/Δ was but some binding to C/C We that a second activity, in S. pombe that recognizes C/C but not other Thus, C/C mismatches are by Cmb1 and Cmb2. 1,2 GpG intrastrand cross-links, produced by cisplatin, are substrates of NER of and of HMG proteins (1Huang J.-C. Hsu D.S. Kazantsev A. Sancar A. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 12213-12217Crossref PubMed Scopus (211) Google Scholar, D.R. Drummond J.T. Murchie A.I. Reardon J.T. Sancar A. Lilley D.M.J. Modrich P. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 6443-6447Crossref PubMed Scopus (372) Google Scholar, D.B. Lippard S.J. Trends Biochem. Sci. 1995; 20: 435-439Abstract Full Text PDF PubMed Scopus (478) Google Scholar, S.J. Kellet P.J. Lippard S.J. Science. 1993; 261: 603-605Crossref PubMed Scopus (180) Google Scholar). We that this lesion is also by the HMG protein that binding by Cmb1 the cytosines opposite the Consistently, but not is by Thus, other HMG and the NER Cmb1 recognizes a of DNA is not well the various proteins normally bases and the types of DNA In the of Cmb1, the presence of cytosines in mismatches as well as in DNA lesions might be for recognition. and some HMG proteins are to in to the drug Whereas binding by the HMG proteins HMG-1 and is to cisplatin from repair (14Huang J.-C. Zamble D.B. Reardon J.T. Lippard S.J. Sancar A. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 10394-10398Crossref PubMed Scopus (341) Google Scholar, S.J. Kellet P.J. Lippard S.J. Science. 1993; 261: 603-605Crossref PubMed Scopus (180) Google Scholar), is that binding of Cmb1 as by of mutant to is an of cisplatin that is as a chemotherapeutic and cross-links produced by transplatin are not by HMG proteins (13Zamble D.B. Lippard S.J. Trends Biochem. Sci. 1995; 20: 435-439Abstract Full Text PDF PubMed Scopus (478) Google Scholar). Consistently, an mutant with transplatin showed no from wild type in (15Brown S.J. Kellet P.J. Lippard S.J. Science. 1993; 261: 603-605Crossref PubMed Scopus (180) Google Scholar). Cmb1 not bind to a intrastrand produced by transplatin, and in to wild the cmb1 mutant is not more sensitive to transplatin not Cmb1 specifically to an lesion no wild type and mutant was when cells were with be to repair of O6meG by an more be to whether Cmb1 has a role in of O6meG from with cmb1 revealed of the of mismatch repair but no in mismatch and J. The on mismatch repair were rather be to of Cmb1 with other proteins of is is able to bind to C/C mismatches Cmb1 as an protein binding to chemically modified DNA and mismatches and such for A repair pathway is the NER which can bases damaged by cisplatin and (1Huang J.-C. Hsu D.S. Kazantsev A. Sancar A. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 12213-12217Crossref PubMed Scopus (211) Google Scholar, 3Sancar A. Annu. Rev. Biochem. 1996; 65: 43-81Crossref PubMed Scopus (960) Google Scholar). that NER genes of S. pombe are in mismatch repair in a The is the repair of C/C mismatches that be by a system P. P. Kohli J. 1993; PubMed Google Scholar, P. Kohli J. 1993; PubMed Google Scholar). We and Schär for and and for on protein We are also to and for and