DNA mismatch repair gene mutS (2.56 kb) was PCR modified and cloned into a secretive prokaryotic expression vector pET32a (+) which carries a N-terminal His.tag + and thioredoxin sequence. MutS protein was expressed with high level after IPTG induction using the strain E. coli AD494(DE3). SDS-PAGE revealed that the expected protein with a molecular weight of 108 kD which is about 35% of the total bacterial proteins is almost soluble. The expected protein was purified directly by immobilized metal (Ni2+) chelation affinity chromatography and the purity is over 90%. MutS protein activity verified using mismatch DNA showed that the expression product can recognize and bind to base-pair mismatch specifically.
Adenosine Triphosphatases ; biosynthesis ; genetics ; isolation & purification ; Bacterial Proteins ; Base Pair Mismatch ; Chromatography, Affinity ; DNA ; metabolism ; DNA Repair ; DNA-Binding Proteins ; Escherichia coli Proteins ; biosynthesis ; genetics ; isolation & purification ; Magnesium ; pharmacology ; Molecular Weight ; MutS DNA Mismatch-Binding Protein ; Recombinant Proteins ; biosynthesis

Development of controllable hypermutable cells can greatly benefit understanding and harnessing microbial evolution. However, there have not been any similar systems developed for Clostridium, an important bacterial genus. Here we report a novel two-step strategy for developing controllable hypermutable cells of Clostridium acetobutylicum, an important and representative industrial strain. Firstly, the mutS/L operon essential for methyldirected mismatch repair (MMR) activity was inactivated from the genome of C. acetobutylicum to generate hypermutable cells with over 250-fold increased mutation rates. Secondly, a proofreading control system carrying an inducibly expressed mutS/L operon was constructed. The hypermutable cells and the proofreading control system were integrated to form a controllable hypermutable system SMBMutC, of which the mutation rates can be regulated by the concentration of anhydrotetracycline (aTc). Duplication of the miniPthl-tetR module of the proofreading control system further significantly expanded the regulatory space of the mutation rates, demonstrating hypermutable Clostridium cells with controllable mutation rates are generated. The developed C. acetobutylicum strain SMBMutC2 showed higher survival capacities than the control strain facing butanol-stress, indicating greatly increased evolvability and adaptability of the controllable hypermutable cells under environmental challenges.
Butanols ; pharmacology ; Cell Engineering ; methods ; Clostridium acetobutylicum ; cytology ; drug effects ; genetics ; physiology ; DNA Methylation ; genetics ; DNA Mismatch Repair ; genetics ; Evolution, Molecular ; Genome, Bacterial ; genetics ; MutS DNA Mismatch-Binding Protein ; genetics ; Mutation ; Operon ; genetics ; Stress, Physiological ; drug effects ; genetics

OBJECTIVETo detect the germline mutation of mismatch repair gene (MSH6) in hereditary nonpolyposis colorectal cancer (HNPCC) kindreds fulfilling different clinical criteria.

METHODSThe germline mutations of MSH6 gene were detected by PCR based DNA sequencing in 39 unrelated HNPCC probands fulfilling different clinical criteria in which MSH2 and MLH1 mutations were excluded. The exons with missense mutations were analyzed using PCR sequencing in the germline genomic DNA of 137 healthy persons. The expression of MSH6 protein was detected by Envision immunohistochemistry staining in the tumor tissues of the mutational probands.

RESULTSSix germline mutations of MSH6 gene were detected in 39 probands of Chinese HNPCC kindreds, and the mutations distributed in the exon 4, 6, 9 and 10. Four out of six mutations were missense mutation, one was nonsense mutation and the remaining one was insertion mutation in splice site. The results of sequecing for the exons with above four missense mutations in 137 healthy persons' genomic DNA showed that 5 of 137 persons had the missense mutation of c.3488 A to T at codon 1163 of the 6th exon. The mutational rate was approximately 3.65% (5/137), so the mutation could be a single nucleotide polymorphism (SNP). The remaining missense mutations were not found in any germline genomic DNA of 137 healthy persons. Positive expression of MSH6 protein had been identified in the tumor of the SNP proband while the tumors had negative MSH6 protein expression in the rest probands of germline mutation MSH6 gene. The types of mutations and their potential significance were determined by comparing the following databases: http://www.ncbi.nlm.nih.gov/, http://www.ensembl.org/homo-sapies, and http://www.insight-group.org. Five out of the six mutations had not been reported previously and they were new pathological mutations, the rest one was a new SNP.

CONCLUSIONGermline mutations of MSH6 gene may play an important role in Chinese HNPCC kindreds fulfilling different clinical criteria. It is necessary to analyze the germline mutations of MSH6 gene using sequencing to identify HNPCC families in the probands in which MSH2 and MLH1 mutation were excluded.

Adult ; Asian Continental Ancestry Group ; genetics ; Base Pair Mismatch ; genetics ; Colorectal Neoplasms, Hereditary Nonpolyposis ; genetics ; pathology ; DNA Mutational Analysis ; DNA Repair Enzymes ; genetics ; Female ; Germ-Line Mutation ; genetics ; Humans ; Male ; Middle Aged ; MutS DNA Mismatch-Binding Protein ; genetics ; MutS Homolog 2 Protein ; genetics ; Pedigree ; Polymerase Chain Reaction

OBJECTIVETo study the protein expression pattern of DNA mismatch repair genes hMSH(2), hMLH(1) and the microsatellite instability (MSI) status in the tumor tissue from hereditary nonpolyposis colorectal cancer in the Chinese.

METHODSFifty-eight families fulfilling different clinical criteria including Amsterdam Criteria (AC) (22/24 families, 38 tumors), Japanese Criteria (JC) (12/15 families, 16 tumors) and Bethesda Guidelines (BG) (12/19 patients, 13 tumors) were studied. Monoclonal antibodies against hMSH(2), hMLH(1) proteins and a panel of microsatellite markers (5 loci) including BAT26, BAT25, D2S123, D5S346 and D17S250 were used for study.

RESULTSMSI-H was identified in all 22 (100%) AC tumors, with 81.8% (18/22) showing altered hMSH(2) or hMLH(1) expression; in 14/15 (93.8%) JC cancer, 1/1 (100%) JC adenoma, with 45.5% (5/11) showing altered hMSH(2) or hMLH(1) expression; and in 7/13 (53.8%) BG tumors, with 4/7 showing loss of hMSH(2) or hMLH(1) gene expression.

CONCLUSIONThe frequency of MSI-H and loss of mismatch repair protein are different in the families fulfilling different clinical criteria. Amsterdam Criteria and Japanese Criteria are the two most useful criterion systems for identifying mismatched repair defective tumors. However, Bethesda Guidelines should also be used for detecting more such tumors. The combination of immunohistochemical methods and microsatellite instability analysis is an effective strategy to detect the mismatch repair defective tumors. A close correlation does exist between hMSH(2), hMLH(1) protein expression pattern and MSI status.

Adaptor Proteins, Signal Transducing ; Base Pair Mismatch ; Carrier Proteins ; Colorectal Neoplasms, Hereditary Nonpolyposis ; genetics ; DNA Repair ; DNA-Binding Proteins ; Humans ; Immunohistochemistry ; Microsatellite Repeats ; MutL Protein Homolog 1 ; MutS Homolog 2 Protein ; Neoplasm Proteins ; genetics ; Nuclear Proteins ; Proto-Oncogene Proteins ; genetics

OBJECTIVETo investigate the expression of DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6 and PMS2) in endometrial adenocarcinoma (EC) of patients under 50 years and to explore the relationship between MMR expression and clinicopathological features including body mass index (BMI), histological grade and pathological stage of EC.

METHODSMMR gene expression was investigated by immunohistochemical S-P method in endometrial adenocarcinomas of patients under age of 50. The control groups included complexity atypical hyperplasia endometrium (CAHE), simple hyperplasia endometrium (SHE), normal endometrium (NE) of patients under age of 50 and EC of patients older than 65 years.

RESULTSTwenty seven of 40 EC (67.5%) lost at least one MMR protein expression. Loss of at least one MMR protein expression was seen in 5/15 cases of CAHE, 1/13 SHE and 1/11 NE, respectively (P < 0.01). The rates of loss of expression of MLH1, MSH2, MSH and PMS2 proteins in EC were 52.5%, 12.5%, 35.0%, and 30.0%, respectively. The difference between MLH1 and MSH6 expression among the four groups were significant (P < 0.05), but the expression of MSH2 showed no significant difference among the groups (P = 0.295). The expression of MMR protein had no relationship with histological grade and pathological stage, although loss of MSH6 was more frequently seen in patients of higher BMI.

CONCLUSIONSAbnormal expression of MMR proteins is correlated with the development of EC from complex atypical hyperplasia. With the exception of the correlation of MSH6 expression with higher BMI, the expression of MMR proteins in EC has no significant relationship with histological grade and pathological stage.

Adaptor Proteins, Signal Transducing ; metabolism ; Adenocarcinoma ; genetics ; metabolism ; pathology ; Adenosine Triphosphatases ; metabolism ; Adult ; Body Mass Index ; DNA Mismatch Repair ; DNA Repair Enzymes ; metabolism ; DNA-Binding Proteins ; metabolism ; Endometrial Neoplasms ; genetics ; metabolism ; pathology ; Female ; Humans ; Immunohistochemistry ; Middle Aged ; Mismatch Repair Endonuclease PMS2 ; MutL Protein Homolog 1 ; MutS Homolog 2 Protein ; metabolism ; Neoplasm Grading ; Neoplasm Staging ; Nuclear Proteins ; metabolism

Adaptor Proteins, Signal Transducing ; genetics ; metabolism ; Adenosine Triphosphatases ; genetics ; metabolism ; DNA Mismatch Repair ; DNA Repair Enzymes ; genetics ; metabolism ; DNA-Binding Proteins ; genetics ; metabolism ; Endometrial Neoplasms ; etiology ; genetics ; metabolism ; pathology ; Female ; Genetic Predisposition to Disease ; Humans ; Lynch Syndrome II ; complications ; genetics ; metabolism ; pathology ; Mismatch Repair Endonuclease PMS2 ; MutL Protein Homolog 1 ; MutS Homolog 2 Protein ; genetics ; metabolism ; Mutation ; Nuclear Proteins ; genetics ; metabolism

OBJECTIVETo study the characteristics of germline mutations of hMLH1, hMSH2 and hMSH6 and promoter methylation status of MLH1 in patients with MSI colorectal cancer.

METHODSSequence analysis of germline mutation and promoter methylation of MLH1 in 34 prospective collected patients with MSI colorectal cancer were performed.

RESULTSNineteen out of 34 patients with MSI colorectal cancer were detected with hypermethylation of MLH1,which accounted for 55.9%. 73.7% MSI-H colorectal cancer cases and 33.3% MSI-L colorectal cancer cases were detected with hypermethylation of MLH1 and the difference was significant. Eight germline mutations were found, including 3 MSH6 mutations and 5 MSH2 mutations.

CONCLUSIONThere are some different characteristics of the germline mutations of hMLH1, hMSH2 and hMSH6 and promoter methylation of MLH1 in Chinese MSI colorectal patients.

Adaptor Proteins, Signal Transducing ; genetics ; Aged ; Base Pair Mismatch ; Colorectal Neoplasms ; genetics ; DNA Methylation ; DNA, Neoplasm ; DNA-Binding Proteins ; genetics ; Female ; Germ-Line Mutation ; Humans ; Male ; Microsatellite Instability ; Middle Aged ; MutL Protein Homolog 1 ; MutS Homolog 2 Protein ; genetics ; Nuclear Proteins ; genetics ; Sequence Analysis, DNA

To determine whether family history of cancer may be a risk factor for the mutator phenotype in colorectal cancer, we recruited 143 consecutive colorectal cancer patients with a family history of accompanying cancers not meeting the Amsterdam criteria. Microsatellite instability (MSI) at 5 markers, hMLH1-promoter methylation, and expression of mismatch repair (MMR) proteins (hMLH1, hMSH2, hMSH6, hMPS1, and hPMS2) were determined. Among the relatives of familial colorectal cancer patients, colorectal cancer was the most common tumor type. Of the proband colorectal cancers, 26 (18.2%) showed high-level MSI (MSI-H); 47 additional tumors with mutator phenotype (32.9%) were identified by hMLH1-promoter methylation and/or loss of MMR protein expression. Mutator phenotype was associated with right-sided colon cancer and the type of accompanying cancer. Family history, which was differentially quantified according to the degree of relatives and the type of accompanying cancers, effectively discriminated MSI-H from microsatellite stable (MSS) and low-level microsatellite instability (MSI-L) and mutator phenotypes. Our findings indicate that familial colorectal cancer may be associated with multiple occurrences of colorectal or accompanying cancers and that family history could be correlated with microsatellite instability.
Adaptor Proteins, Signal Transducing/genetics/metabolism ; Adenosine Triphosphatases/metabolism ; Adult ; Aged ; Aged, 80 and over ; Base Sequence ; Colorectal Neoplasms/*genetics/metabolism/pathology ; DNA Methylation ; DNA Mismatch Repair ; DNA Repair Enzymes/metabolism ; DNA, Neoplasm/genetics ; DNA-Binding Proteins/metabolism ; Female ; Humans ; Male ; *Microsatellite Instability ; Middle Aged ; MutS Homolog 2 Protein/metabolism ; Neoplasm Proteins/metabolism ; Nuclear Proteins/genetics/metabolism ; Phenotype ; Promoter Regions, Genetic ; Risk Factors

OBJECTIVEIn this study, we assayed promoter hypermethylation and protein expression of the mismatch repair gene (MMR) hMLH1 and hMSH2 in gestational trophoblastic diseases to understand the significance of MMR promoter methylation and expression in the pathogenesis and malignant transformation of hydatidiform mole.

METHODSDNA was extracted from chorion of early pregnancies, partial hydatidiform moles, complete hydatidiform moles, and invasive moles were over digested by methylation sensitive endonuclease Hpa II. Then the promoters were amplificated by polymerase chain reaction. The protein was detected by immunohistochemistry.

RESULTSIn the normal placenta, neither hMLH1 nor hMSH2 promoter methylation was detected. Expression of hMLH1 and hMSH2 in cytotrophoblasts was strongly positive, and that was negative or weakly positive in syncytiotrophobasts. In all normal chorion, expression of hMLH1 and hMSH2 in cytotrophoblasts was strongly positive. In partial hydatidiform mole and complete hydatidiform mole, the methylation of hMLH1 and hMSH2 promoters was significantly higher than that of early placenta (P < 0.05), and the protein expression in cytotrophoblasts was significantly lower (P < 0.05). In the invasive mole, hMLH1 and hMSH2 promoter methylation were not significantly different as compared with the partial hydatidiform mole and complete hydatidiform mole (P > 0.05). Expression of hMLH1 in the invasive mole (54.5%, 6/11) was not significantly different as compared with the partial hydatidiform mole and complete hydatidiform mole (P > 0.05). But expression of hMSH2 in the invasive mole (36.4%, 4/11) was weaker than that in complete hydatidiform mole (P = 0.044). Promoter methylation and less expression of hMSH2 had correlations in complete hydatidiform mole or invasive mole.

CONCLUSIONSStrong expressions of hMLH1 and hMSH2 in the cytotrophoblasts of normal placenta may keep the genome stability. Promoter methylation and down-regulation of hMLH1 and hMSH2 are probably involved in the pathogenesis of hydatidiform mole.

Adaptor Proteins, Signal Transducing ; Adult ; Base Pair Mismatch ; genetics ; Carrier Proteins ; DNA Methylation ; DNA Repair ; DNA-Binding Proteins ; biosynthesis ; Female ; Humans ; Hydatidiform Mole ; genetics ; pathology ; Hydatidiform Mole, Invasive ; genetics ; pathology ; Middle Aged ; MutL Protein Homolog 1 ; MutS Homolog 2 Protein ; Neoplasm Proteins ; biosynthesis ; Nuclear Proteins ; Pregnancy ; Promoter Regions, Genetic ; genetics ; Proto-Oncogene Proteins ; biosynthesis ; Uterine Neoplasms ; genetics ; pathology

OBJECTIVETo explore the relationship between DNA mismatch repair (MMR) and clinicopathologic features and prognosis in patients with stages II and III colon cancers.

METHODSThe clinical and pathological data of 440 patients with stage II/III colon cancer after radical resection were retrospectively reviewed and analyzed. Immunohistochemical staining was used to assess the expression of MMR proteins (MLH1, MSH2, MSH6 and PMS2), and the correlation between DNA MMR and clinicopathological features and prognosis of colon cancers was analyzed.

RESULTSOf the 440 tumor samples tested for DNA mismatch repair status, 90 (20.5%) demonstrated defective DNA mismatch repair and 350 (79.5%) had proficient DNA mismatch repair. Defective DNA mismatch repair (dMMR) was associated with young patients (≤ 60), proximal colon cancer, stage II, poorly differentiated adenocarcinoma and mucinous adenocarcinoma (P<0.05 for all). Among the 440 patients, 126 (28.6%) cases had recurrence or metastasis and 93 (21.1%) died during the median follow-up of 61.0 months. The five-year disease-free survival (DFS) rate was 82.2% among the patients with tumor exhibiting dMMR, significantly higher than that in patients with tumors exhibiting pMMR (68.9%, P=0.02). The univariate and mutlivariate analyses showed that the MMR status is an independent factor affecting 5-year disease-free survival and overall survival (OS) in colon cancer patients (P<0.05 for both).

CONCLUSIONSDefective DNA mismatch repair (dMMR) is associated with patients with proximal colon cancer, stage II and poorly defferentiated adenocarcinoma and mucinous adenocarcinoma. The prognosis for patients with dMMR is better than those with pMMR. dMMR may be a useful biomarker for the prognosis of colon cancer.

Adaptor Proteins, Signal Transducing ; metabolism ; Adenocarcinoma ; genetics ; metabolism ; mortality ; pathology ; Adenocarcinoma, Mucinous ; genetics ; metabolism ; mortality ; pathology ; Adenosine Triphosphatases ; metabolism ; Age Factors ; Analysis of Variance ; Colonic Neoplasms ; genetics ; metabolism ; mortality ; pathology ; DNA Mismatch Repair ; DNA Repair Enzymes ; metabolism ; DNA-Binding Proteins ; metabolism ; Disease-Free Survival ; Humans ; Mismatch Repair Endonuclease PMS2 ; MutL Protein Homolog 1 ; MutS Homolog 2 Protein ; metabolism ; Neoplasm Recurrence, Local ; Nuclear Proteins ; metabolism ; Prognosis ; Retrospective Studies ; Survival Rate