Search results for "Transferase"
showing 10 items of 1030 documents
Apoptosis in malignant glioma cells triggered by the temozolomide-induced DNA lesion O6-methylguanine
2006
Methylating drugs such as temozolomide (TMZ) are widely used in the treatment of brain tumours (malignant gliomas). The mechanism of TMZ-induced glioma cell death is unknown. Here, we show that malignant glioma cells undergo apoptosis following treatment with the methylating agents N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and TMZ. Cell death determined by colony formation and apoptosis following methylation is greatly stimulated by p53. Transfection experiments with O(6)-methylguanine-DNA methyltransferase (MGMT) and depletion of MGMT by O(6)-benzylguanine showed that, in gliomas, the apoptotic signal originates from O(6)-methylguanine (O(6)MeG) and that repair of O(6)MeG by MGMT prevent…
O6-methylguanine DNA methyltransferase and p53 status predict temozolomide sensitivity in human malignant glioma cells
2006
Temozolomide (TMZ) is a methylating agent which prolongs survival when administered during and after radiotherapy in the first-line treatment of glioblastoma and which also has significant activity in recurrent disease. O6-methylguanine DNA methyltransferase (MGMT) is a DNA repair enzyme attributed a role in cancer cell resistance to O6-alkylating agent-based chemotherapy. Using a panel of 12 human glioma cell lines, we here defined the sensitivity to TMZ in acute cytotoxicity and clonogenic survival assays in relation to MGMT, mismatch repair and p53 status and its modulation by dexamethasone, irradiation and BCL-X(L). We found that the levels of MGMT expression were a major predictor of T…
Substrate promiscuity in DNA methyltransferase M.PvuII. A mechanistic insight
2012
M.PvuII is a DNA methyltransferase from the bacterium Proteus vulgaris that catalyzes methylation of cytosine at the N4 position. This enzyme also displays promiscuous activity catalyzing methylation of adenine at the N6 position. In this work we use QM/MM methods to investigate the reaction mechanism of this promiscuous activity. We found that N6 methylation in M.PvuII takes place by means of a stepwise mechanism in which deprotonation of the exocyclic amino group is followed by the methyl transfer. Deprotonation involves two residues of the active site, Ser53 and Asp96, while methylation takes place directly from the AdoMet cofactor to the target nitrogen atom. The same reaction mechanism…
Inhibition of O6-Methylguanine-DNA Methyltransferase by Glucose-Conjugated Inhibitors: Comparison with Nonconjugated Inhibitors and Effect on Fotemus…
2004
The DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) is an important suicide enzyme involved in the defense against O(6)-alkylating mutagens. It also plays a role in the resistance of tumors to anticancer drugs targeting the O(6)-position of guanine, such as temozolomide and fotemustine. Several potent MGMT inhibitors have been developed sensitizing cells to O(6)-alkylating agents. Aimed at targeting MGMT inhibitors to tumor cells, we synthesized MGMT inhibitory compounds conjugated with glucose to improve uptake in tumor cells. Here, we compared O(6)-benzylguanine, O(6)-2-fluoropyridinylmethylguanine (O(6)FPG), O(6)-3-iodobenzylguanine, O(6)-4-bromothenylguanine, and O(6)…
A New Nuclear Function of the Entamoeba histolytica Glycolytic Enzyme Enolase: The Metabolic Regulation of Cytosine-5 Methyltransferase 2 (Dnmt2) Act…
2009
Cytosine-5 methyltransferases of the Dnmt2 family function as DNA and tRNA methyltransferases. Insight into the role and biological significance of Dnmt2 is greatly hampered by a lack of knowledge about its protein interactions. In this report, we address the subject of protein interaction by identifying enolase through a yeast two-hybrid screen as a Dnmt2-binding protein. Enolase, which is known to catalyze the conversion of 2-phosphoglycerate (2-PG) to phosphoenolpyruvate (PEP), was shown to have both a cytoplasmatic and a nuclear localization in the parasite Entamoeba histolytica. We discovered that enolase acts as a Dnmt2 inhibitor. This unexpected inhibitory activity was antagonized by…
FICC-Seq: a method for enzyme-specified profiling of methyl-5-uridine in cellular RNA.
2019
AbstractMethyl-5-uridine (m5U) is one the most abundant non-canonical bases present in cellular RNA, and in yeast is found at position U54 of tRNAs where modification is catalysed by the methyltransferase Trm2. Although the mammalian enzymes that catalyse m5U formation are yet to be identified via experimental evidence, based on sequence homology to Trm2, two candidates currently exist, TRMT2A and TRMT2B. Here we developed a genome-wide single-nucleotide resolution mapping method, Fluorouracil-Induced-Catalytic-Crosslinking-Sequencing (FICC-Seq), in order to identify the relevant enzymatic targets. We demonstrate that TRMT2A is responsible for the majority of m5U present in human RNA, and t…
Unraveling the Reaction Mechanism of Enzymatic C5-Cytosine Methylation of DNA. A Combined Molecular Dynamics and QM/MM Study of Wild Type and Gln119 …
2016
M.HhaI is a DNA methyltransferase from Haemophilus hemolyticus that catalyzes the transfer of a methyl group from S-adenosyl-l-methionine (SAM) to the C5 position of a cytosine. This enzyme is a paradigmatic model for C5 DNA methyltransferases due to its major homology to mammalian enzymes and to the availability of high-resolution structures of the DNA–enzyme complex. In spite of the number of experimental and theoretical analyses carried out for this system, many mechanistic details remain unraveled. We have used full atomistic classical molecular dynamics simulations to explore the protein–SAM–DNA ternary complex, where the target cytosine base is flipped out into the active site for bot…
Synthesis and antiproliferative activity of 3-(2-chloroethyl)-5-methyl-6-phenyl-8-(trifluoromethyl)-5,6-dihydropyrazolo[3,4-f][1,2,3,5]tetrazepin-4-(…
2015
Based on the encouraging results found for 3,5-dimethyl-6-phenyl-8-(trifluoromethyl)-5,6-dihydropyrazolo[3,4-f][1,2,3,5]tetrazepin-4-(3H)-one 7 previously tested by us, as well as the consideration that heterocycle fused tetrazepinones bearing the 2-chloroethyl substituent show a better cytotoxic profile than temozolomide and mitozolomide against human cancer cell lines which express the DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT), in this paper we report the multistep synthesis and the biological study of 3-(2-cloroethyl)-5-methyl-6-phenyl-8-(trifluoromethyl)-5,6-dihydropyrazolo[3,4-f][1,2,3,5]tetrazepin-4-(3H)-one 10. Like compound 7, it was active on P-glycoprotein e…
Association of Maternal Secretor Status and Human Milk Oligosaccharides With Milk Microbiota: An Observational Pilot Study
2019
Background and Objectives: Breast milk contains several bioactive factors including oligosaccharides (HMO) and microbes that shape the infant gut microbiota. HMO profile is determined by secretor status, however their influence on milk microbiota is still uncovered. This study is aimed to determine the impact of the FUT2 genotype on the milk microbiota during the first month of lactation and the association with HMO. Methods: Milk microbiota from 25 healthy lactating women was determined by quantitative PCR and 16S gene pyrosequencing. Secretor genotype was obtained by PCR-RFLPs and by HMO identification and quantification. Results: The most abundant bacteria were Staphylococcus and Strepto…
Evidence of a New MoYpd1p Phosphotransferase Isoform in the Multistep Phosphorelay System of Magnaporthe oryzae
2021
Different external stimuli are perceived by multiple sensor histidine kinases and transmitted by phosphorylation via the phosphotransfer protein Ypd1p in the multistep phosphorelay system of the high osmolarity glycerol signaling pathway of filamentous fungi. How the signal propagation takes place is still not known in detail since multiple sensor histidine kinase genes in most filamentous fungi are coded in the genome, whereas only one gene for Ypd1p exists. That raises the hypothesis that various Ypd1p isoforms are produced from a single gene sequence, perhaps by alternative splicing, facilitating a higher variability in signal transduction. We found that the mRNA of MoYPD1 in the rice bl…