Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Most susceptibility to colorectal cancer (CRC) is not accounted for by known risk factors. Because MLH1, MSH2 and MSH6 mutations underlie high-penetrance CRC susceptibility in hereditary nonpolyposis colon cancer (HNPCC), we hypothesized that attenuated alleles might also underlie susceptibility to sporadic CRC. We looked for gene variants associated with HNPCC in Israeli probands with familial CRC unstratified with respect to the microsatellite instability (MSI) phenotype. Association studies identified a new MLH1 variant (415G-->C, resulting in the amino acid substitution D132H) in approximately 1.3% of Israeli individuals with CRC self-described as Jewish, Christian and Muslim. MLH1 415C confers clinically significant susceptibility to CRC. In contrast to classic HNPCC, CRCs associated with MLH1 415C usually do not have the MSI defect, which is important for clinical mutation screening. Structural and functional analyses showed that the normal ATPase function of MLH1 is attenuated, but not eliminated, by the MLH1 415G-->C mutation. The new MLH1 variant confers a high risk of CRC and identifies a previously unrecognized mechanism in microsatellite-stable tumors. These studies suggest that variants of mismatch repair proteins with attenuated function may account for a higher proportion of susceptibility to sporadic microsatellite-stable CRC than previously assumed.
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PMID:The MLH1 D132H variant is associated with susceptibility to sporadic colorectal cancer. 1518 98

Mutations in mismatch repair (MMR) genes predispose to hereditary nonpolyposis colon cancer. Those leading to truncated proteins bring about a MMR defect, but phenotypes of missense mutations are harder to predict especially if they do not affect conserved residues. Several systems capable of predicting the phenotypes of MMR missense mutations were described. We deployed one of these to study the MMR defect in MT1 cells, which carry mutations in both alleles of the hMSH6 gene. In one, an A-->T transversion brings about an Asp(1213)Val amino acid change in the highly conserved ATP binding site, whereas the other carries a G-->A transition, which brings about a Val(1260)Ile change at a nonconserved site. The hMSH2/hMSH6 (hMutS alpha) heterodimers carrying these mutations were expressed in the baculovirus system and tested in in vitro MMR assays. As anticipated, the Asp(1213)Val mutation inactivated MMR by disabling the variant hMutS alpha from translocating along the DNA. In contrast, the recombinant Val(1260)Ile variant displayed wild-type activity. Interestingly, partial proteolytic analysis showed that this heterodimer was absent from MT1 extracts, although both hMSH6 alleles in MT1 cells could be shown to be transcribed with an efficiency similar to each other and to that seen in control cells. The MMR defect in MT1 cells is thus the compound result of one mutation that inactivates the ATPase function of hMutS alpha and a second mutation that apparently destabilizes the Val(1260)Ile hMSH6 protein in human cells in vivo.
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PMID:Characterization of the mismatch repair defect in the human lymphoblastoid MT1 cells. 1593 Feb 69

Lynch syndrome or hereditary nonpolyposis colorectal cancer (HNPCC) is a hereditary syndrome with genetic heterogeneity. The disease is caused by mutations or epigenetic silencing in DNA mismatch repair genes, MLH1, MSH2, MSH6, PMS2 and MLH3, although the vast majority of cases correspond to mutations of MLH1 and MSH2. We herein describe a nucleotide change, c.2063T>G in exon 13 of the MSH2 gene, present in families that fulfill the Amsterdam criteria for Lynch syndrome and originate from northern Tenerife (Canary Islands-Spain). This mutation is expected to result in a nonconservative amino acid change, M688R, at the ATPase domain of the MSH2 protein. We found five large families with this mutation, and about half the individuals heterozygous for M688R developed malignancies by the sixth decade of life. In many cases analyzed, their tumors revealed loss of the normal allele, being homozygous for M688R. There is an evidence of historical isolation for the population studied, which could have favored a considerable genetic drift. The presence of the same mutation and the disease associated-haplotype conservation in families not directly related can be probably the consequence of a bottleneck in the founding of this population (rather than a relatively recent founding of the mutation).
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PMID:New founding mutation in MSH2 associated with hereditary nonpolyposis colorectal cancer syndrome on the Island of Tenerife. 1650 24

Mutations in the human DNA mismatch repair (MMR) gene MLH1 are associated with hereditary nonpolyposis colorectal cancer (Lynch syndrome, HNPCC) and a significant proportion of sporadic colorectal cancer. The inactivation of MLH1 results in the accumulation of somatic mutations in the genome of tumor cells and resistance to the genotoxic effects of a variety of DNA damaging agents. To study the effect of MLH1 missense mutations on cancer susceptibility, we generated a mouse line carrying the recurrent Mlh1(G67R) mutation that is located in one of the ATP-binding domains of Mlh1. Although the Mlh1(G67R) mutation resulted in DNA repair deficiency in homozygous mutant mice, it did not affect the MMR-mediated cellular response to DNA damage, including the apoptotic response of epithelial cells in the intestinal mucosa to cisplatin, which was defective in Mlh1(-/-) mice but remained normal in Mlh1(G67R/G67R) mice. Similar to Mlh1(-/-) mice, Mlh1(G67R/G67R) mutant mice displayed a strong cancer predisposition phenotype. However, in contrast to Mlh1(-/-) mice, Mlh1(G67R/G67R) mutant mice developed significantly fewer intestinal tumors, indicating that Mlh1 missense mutations can affect MMR tumor suppressor functions in a tissue-specific manner. In addition, Mlh1(G67R/G67R) mice were sterile because of the inability of the mutant Mlh1(G67R) protein to interact with meiotic chromosomes at pachynema, demonstrating that the ATPase activity of Mlh1 is essential for fertility in mammals.
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PMID:Distinct effects of the recurrent Mlh1G67R mutation on MMR functions, cancer, and meiosis. 1833 3

Missense mutations of the DNA mismatch repair gene MLH1 are found in a significant fraction of patients with Lynch syndrome (hereditary nonpolyposis colorectal cancer, HNPCC) and their pathogenicity often remains unclear. We report here all 88 MLH1 missense variants identified in families from the German HNPCC consortium with clinical details of these patients/families. We investigated 23 MLH1 missense variants by two functional in vivo assays in yeast; seven map to the ATPase and 16 to the protein interaction domain. In the yeast-2-hybrid (Y2H) assay three variants in the ATPase and twelve variants in the interaction domain showed no or a reduced interaction with PMS2; seven showed a normal and one a significantly higher interaction. Using the Lys2A (14) reporter system to study the dominant negative mutator effect (DNE), 16 variants showed no or a low mutator effect, suggesting that these are nonfunctional, three were intermediate and four wild type in this assay. The DNE and Y2H results were concordant for all variants in the interaction domain, whereas slightly divergent results were obtained for variants in the ATPase domain. Analysis of the stability of the missense proteins in yeast and human embryonic kidney cells (293T) revealed a very low expression for seven of the variants in yeast and for nine in human cells. In total 15 variants were classified as deleterious, five were classified as variants of unclassified significance (VUS) and three were basically normal in the functional assays, P603R, K618R, Q689R, suggesting that these are neutral.
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PMID:Missense variants in hMLH1 identified in patients from the German HNPCC consortium and functional studies. 2140 17

DNA mismatch repair (MMR) greatly contributes to genome integrity via the correction of mismatched bases that are mainly generated by replication errors. Postreplicative MMR excises a relatively long tract of error-containing single-stranded DNA. MutL is a widely conserved nicking endonuclease that directs the excision reaction to the error-containing strand of the duplex by specifically nicking the daughter strand. Because MutL apparently exhibits nonspecific nicking endonuclease activity in vitro, the regulatory mechanism of MutL has been argued. Recent studies suggest ATP-dependent conformational and functional changes of MutL, indicating that the regulatory mechanism involves the ATP binding and hydrolysis cycle. In this study, we investigated the effect of ATP binding on the structure of MutL. First, a cross-linking experiment confirmed that the N-terminal ATPase domain physically interacts with the C-terminal endonuclease domain. Next, hydrogen/deuterium exchange mass spectrometry clarified that the binding of ATP to the N-terminal domain induces local structural changes at the catalytic sites of MutL C-terminal domain. Finally, on the basis of the results of the hydrogen/deuterium exchange experiment, we successfully identified novel regions essential for the endonuclease activity of MutL. The results clearly show that ATP modulates the nicking endonuclease activity of MutL via structural rearrangements of the catalytic site. In addition, several Lynch syndrome-related mutations in human MutL homolog are located in the position corresponding to the newly identified catalytic region. Our data contribute toward understanding the relationship between mutations in MutL homolog and human disease.
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PMID:Evidence for ATP-dependent structural rearrangement of nuclease catalytic site in DNA mismatch repair endonuclease MutL. 2195 55

Lynch syndrome (Hereditary nonpolyposis colorectal cancer, HNPCC) is an inherited disease with variable phenotype causing the development of colon cancer and other malignancies. The basis of the disease is believed to be the mismatch repair gene mutations. Genetic screening has been performed among the patients who have undergone surgery for colon cancer at the University of Debrecen, Department of Surgery. Tumor samples of the screened patients were submitted to immunohistochemistry on hMLH1, hMSH2 and hMSH6 genes, microsatellite instability testing, followed by sequencing and multiple ligation dependent probe amplification. Three families were identified with the missense mutation c.143A>C (p.Q48P) of hMLH1 gene. In one of the families a segregation analysis of this particular variant was also accomplished. The segregation analysis revealed a clear correlation between the tumor cases and the occurrence of this mutation. However, none of the analyzed 100 healthy controls demonstrated the same aberration. There is only one published evidence in the literature about the presence of this rare variant in any population. The Gln to Pro switch in the ATPase domain, a conservative region of the hMLH1 gene, creates significant changes in the protein structure. These results indicate that this mutation is the abnormality responsible for the patients' phenotype and it is feasible that this particular aberration occurs more frequently among Hungarian Lynch syndrome patients.
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PMID:Q48P mutation in the hMLH1 gene associated with Lynch syndrome in three Hungarian families. 2239 73

The hMSH2(M688R) mismatch repair (MMR) gene mutation has been found in five large families from Tenerife, Spain, suggesting it is a Lynch syndrome or hereditary non-polyposis colorectal cancer (LS/HNPCC) founder mutation. In addition to classical LS/HNPCC tumors, these families present with a high incidence of central nervous system (CNS) tumors normally associated with Turcot or constitutional mismatch repair deficiency (CMMR-D) syndromes. Turcot and CMMR-D mutations may be biallelic, knocking out both copies of the MMR gene. The hMSH2(M688R) mutation is located in the ATP hydrolysis (ATPase) domain. We show that the hMSH2(M688R)-hMSH6 heterodimer binds to mismatched nucleotides but lacks normal ATP functions and inhibits MMR in vitro when mixed with the wild-type (WT) heterodimer. Another alteration that has been associated with LS/HNPCC, hMSH2(M688I)-hMSH6, displays no identifiable differences with the WT heterodimer. Interestingly, some extracolonic tumors from hMSH2(M688R) carriers may express hMSH2-hMSH6, yet display microsatellite instability (MSI). The functional analysis along with variability in tumor expression and the high incidence of CNS tumors suggests that hMSH2(M688R) may act as a dominant negative in some tissues, while the hMSH2(M688I) is most likely a benign polymorphism.
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PMID:The hMSH2(M688R) Lynch syndrome mutation may function as a dominant negative. 2273 24

Lynch syndrome (LS) is an autosomal dominant cancer-susceptibility disease caused by inactivating germline mutations in mismatch repair (MMR) genes. Variants of unknown significance (VUS) are often detected in mutational analysis of MMR genes. Here we describe a large family fulfilling Amsterdam I criteria carrying two rare VUS in the MLH1 gene: c.121G > C (p.D41H) and c.2128A > G (p.N710D). Collection of clinico-pathological data, multifactorial analysis, in silico predictions, and functional analyses were used to elucidate the clinical significance of the identified MLH1 VUS. Only the c.121G > C variant cosegregated with LS-associated tumors in the family. Diagnosed colorectal tumors were microsatellite unstable although immunohistochemical staining revealed no loss of MMR proteins expression. Multifactorial likelihood analysis classified c.2128A > G as a non-pathogenic variant and c.121G > C as pathogenic. In vitro functional tests revealed impaired MMR activity and diminished expression of c.121G > C. Accordingly, the N710 residue is located in the unconserved MLH1 C-terminal domain, whereas D41 is highly conserved and located in the ATPase domain. The obtained results will enable adequate genetic counseling of c.121G > C and c.2128A > G variant carriers and their families. Furthermore, they exemplify how cumulative data and comprehensive analyses are mandatory to refine the classification of MMR variants.
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PMID:Detailed characterization of MLH1 p.D41H and p.N710D variants coexisting in a Lynch syndrome family with conserved MLH1 expression tumors. 2506 Jun 79

Lynch syndrome (LS) is an autosomal dominant inherited disorder that is associated with an increased predisposition to certain cancers caused by loss-of-function mutations in one of four DNA mismatch repair (MMR) genes (MLH1, MSH2, MSH6, or PMS2). The diagnosis of LS is often challenged by the identification of missense mutations where the functional effects are not known. These are termed variants of uncertain significance (VUSs) and account for 20%-30% of noncoding and missense mutations. VUSs cause ambiguity during clinical diagnosis and hinder implementation of appropriate medical management. In the current study, we focus on the functional and biological consequences of two nonsynonymous VUSs in PMS2. These variants, c.620G>A and c.123_131delGTTAGTAGA, result in the alteration of glycine 207 to glutamate (p.Gly207Glu) and the deletion of amino acid residues 42-44 (p.Leu42_Glu44del), respectively. While the PMS2 p.Gly207Glu variant retains in vitro MMR and ATPase activities, PMS2 p.Leu42_Glu44del appears to lack such capabilities. Structural and biophysical characterization using circular dichroism, small-angle X-ray scattering, and X-ray crystallography of the N-terminal domain of the PMS2 variants indicate that the p.Gly207Glu variant is properly folded similar to the wild-type enzyme, whereas p.Leu42_Glu44del is disordered and prone to aggregation.
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PMID:Biochemical and structural characterization of two variants of uncertain significance in the PMS2 gene. 3065 81


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