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:2.1.1.37 (DNA methyltransferase)
4,983 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of the primary mammalian DNA methyltransferase, DNMT1, in maintaining CpG island methylation in human colon cancer cells has recently been questioned. This controversy has arisen from discrepancies between genetic knockout and RNA interference-mediated knockdown studies. Here, we re-examined the RNA interference-based approach and found that hypermethylation of single-copy genes is maintained in cells transiently and stably depleted of DNMT1.
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PMID:CpG island hypermethylation is maintained in human colorectal cancer cells after RNAi-mediated depletion of DNMT1. 1515 41

Previous studies showed that progesterone receptor (PR), one of the hormone receptor superfamily, was only connected with the sex-correlated cancers such as breast cancer, endometrial cancer, prostate cancer, etc. This article deals with the PR gene in leukemia. We investigated the methylation status and the expression of the two different PR isoforms, PRA and PRB, in three leukemia cancer cell lines using methylation-specific polymerase chain reaction (MSP-PCR) and reverse transcription-PCR. The correlation of PR methylation and expression together with DNA methyltransferase (DNMT1) was further studied. We found that DNMT1 is required to maintain CpG methylation and aberrant gene silencing of PR gene in human leukemia cancer cells. The activity of 5-aza-2'-deoxycytidine in demethylation and gene reactivation may be through depleting cellular DNMT1 levels. In addition, extensive methylation of PRA and PRB was also observed in leukemia samples. Our results suggest that PR CpG island aberrant hypermethylation could be one molecular and genetic alteration in leukemia.
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PMID:Progesterone receptor gene inactivation and CpG island hypermethylation in human leukemia cancer cells. 1517 46

Despite the wide range of probes commercially available for interphase fluorescence in situ hybridisation (FISH), the supply of locus-specific probes is limited to genes or chromosomal regions commonly altered in genetic diseases or during carcinogenesis. Generation of these probes is therefore desirable to accommodate individual research requirements. Hence, we detail the methodology required to design and produce custom locus-specific interphase FISH probes for any human genomic region of interest and their application was illustrated in cytogenetic investigations of Barrett's tumourigenesis. Previously utilising FISH, we observed that Barrett's tissues demonstrated chromosome 4 hyperploidy [Gut 52 (2003) 623], but as centromeric probes were used in this analysis, it was not known if the whole chromosome was amplified. We consequently generated single-copy sequence probes for the 4p16.3 and 4q35.1 subtelomeric loci. Multicolour FISH was subsequently performed on interphase preparations originating from patients with Barrett's esophagus at varying histological grades, thus demonstrating the whole region of chromosome 4 was amplified within the tissues. Additionally, probes for the DNA methyltransferase genes were produced to determine if gene dosage alterations were responsible for increasing methylation activity during Barrett's neoplastic progression. No significant alterations at the DNMT1 and DNMT3a loci were detected. An increased copy number of these genes is therefore not the basis for the hypermethylation commonly observed in this premalignant lesion.
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PMID:Generation of locus-specific probes for interphase fluorescence in situ hybridisation--application in Barrett's esophagus. 1521 47

Chemotherapy using DNA intercalators is one of the most successful approaches to cancer treatment. Although DNA intercalators are believed to inhibit DNA polymerases and topoisomerases, resulting in the induction of apoptosis in tumor cells, other factors potentially inhibited by the anthracycline antibiotics remain to be elucidated. Herein, we show that the enzymatic activity of DNMT1, the primary DNA methyltransferase in mammalian cells, is inhibited by DNA intercalators, such as doxorubicin, in an in vitro assay. Enzymatic analyses indicate that doxorubicin inhibits the catalytic activity of DNMT1 via DNA intercalation. We also found that apoptosis was induced in DNMT1(+/+) HCT116 cells by only a limited range of doxorubicin dose, meaning that apoptotic cell death is "conditional" with respect to the concentration of the DNA intercalating drug. It is noteworthy that conditional apoptosis is not observed in human colorectal cancer cells lacking DNMT1 but can be induced in DNMT1(-/-) cells by transfection of a plasmid expressing DNMT1. Our results suggest that DNMT1 is one of the major targets of doxorubicin resulting in drug-induced apoptosis in human cancer cells. We propose that expression levels of DNMT1 in tumor cells may affect the effectiveness of doxorubicin in chemotherapy.
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PMID:Doxorubicin inhibits DNMT1, resulting in conditional apoptosis. 1534 41

MHC peptides derived from tumor-associated antigens (TAAs) can serve as the basis for the development of immunotherapeutics to treat human malignancies. Previously, we identified novel HLA-A*0201 (HLA-A2)-restricted peptides recovered from soluble HLA molecules secreted by human tumor cell lines, transfected with truncated genes of HLA-A2 and HLA-B7. Here, 4 candidate peptides eluted from soluble HLA-A2 were selected on the basis of their precursor proteins being TAAs. Peptide p1028 (GLIEKNIEL), derived from DNA methyltransferase I (DNMT-1), which is overexpressed in various human tumors, showed the highest affinity to HLA-A2 and was relatively abundant in the sMHC/peptide complexes of all transfected breast, ovarian and prostate cancer cell lines. Peptide p1028-specific CTLs were generated in vitro and shown to efficiently lyse not only target cells pulsed with the peptide but also HLA-A2-positive breast cancer cell lines MDA-231 and MCF-7. The peptide induced IFN-gamma production in CTLs, which were selectively stained by a p1028 tetramer. Since DNMT-1 is a widely expressed tumor-associated enzyme, the novel DNMT-1-derived, HLA-A2-restricted peptide GLIEKNIEL identified here may provide a suitable candidate for a therapeutic cancer vaccine.
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PMID:A novel DNA methyltransferase I-derived peptide eluted from soluble HLA-A*0201 induces peptide-specific, tumor-directed cytotoxic T cells. 1538 68

Fetal hemoglobin (HbF, alpha2gamma2) decreases polymerization of sickle hemoglobin, and high levels correlate with decreased morbidity and mortality in sickle cell disease (SCD). Therefore, a therapeutic goal for patients with SCD is pharmacologic reactivation of HbF. Decreased HbF production is associated with DNA methylation (by DNA methyltransferase [DNMT]) at the gamma-globin (HbF) gene promoter. The cytosine analogs 5-azacytidine and 5-aza-2'-deoxycytidine (decitabine) hypomethylate DNA by inhibiting DNMT. In early studies, 5-azacytidine produced significant HbF elevations in patients with thalassemia and SCD, but clinical development of this class of agent was halted after a poorly controlled animal study suggested that 5-azacytidine might be carcinogenic. However, the majority of preclinical studies with decitabine have suggested a chemopreventive rather than carcinogenic effect. Furthermore, decitabine, unlike 5-azacytidine, does not incorporate into RNA and is a more directed DNA-hypomethylating agent. Therefore, we have pursued studies of decitabine to pharmacologically reactivate HbF in patients with SCD. In phase I/II studies, decitabine at DNA-hypomethylating, but noncytotoxic, doses was well tolerated and effective at increasing HbF and total hemoglobin levels both in patients who had and had not responded to prior hydroxyurea therapy. In treated patients, there were marked improvements in a range of surrogate clinical endpoints measuring red blood cell adhesion, endothelial damage, and coagulation pathway activity. Pharmacologic reactivation of HbF through DNA hypomethylation holds promise as an effective disease-modifying intervention for patients with SCD. Larger studies are required to confirm the safety and effectiveness of decitabine with chronic use, and to more clearly establish its role in patients with SCD.
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PMID:Clinical studies with fetal hemoglobin-enhancing agents in sickle cell disease. 1553 52

The formation of multiprotein complexes is l'ordre du jour in regulatory pathways. In this issue of Oncogene, Reale et al. report the formation of a particularly sophisticated complex of two important regulatory enzymes, DNMT1 (DNA methyltransferase-1) and PARP-1 (poly(ADP-ribose)polymerase-1). The former evolved with a specific sequence motif binding the enzymatic product of the latter. The product, poly(ADP-ribose), bonds the two partners into a heterodimeric complex and, as a consequence, the catalytic function of DNMT1 is silenced. Thus, PARP-1 becomes a conditional negative regulator of DNMT1. In a larger perspective, Reale et al. highlight the potential role of PARP-1 as a co-regulator of DNA methylation leading to epigenetic reprogramming of cancer cells.
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PMID:Poly(ADP-ribose): a co-regulator of DNA methylation? 1563 86

We provided evidence that competitive inhibition of poly(ADP-ribose) polymerases in mammalian cells treated with 3-aminobenzamide causes DNA hypermethylation in the genome and anomalous hypermethylation of CpG islands. The molecular mechanism(s) connecting poly(ADP-ribosyl)ation with DNA methylation is still unknown. Here we show that DNMT1 is able to bind long and branched ADP-ribose polymers in a noncovalent way. Binding of poly ADP-ribose on DNMT1 inhibits DNA methyltransferase activity. Co-immunoprecipitation reactions indicate that PARP1 and DNMT1 are associated in vivo and that in this complex PARP1 is present in its ADP-ribosylated isoform. We suggest that this complex is catalytically inefficient in DNA methylation.
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PMID:Modulation of DNMT1 activity by ADP-ribose polymers. 1563 87

Tumor suppressor gene silencing by DNA hypermethylation contributes to tumorigenesis in many tumor types. This aberrant methylation may be due to increased expression and activity of DNA methyltransferases, which catalyze the transfer of methyl groups from S-adenosylmethionine to cytosines in CpG dinucleotides. Elevated expression of the maintenance DNA methyltransferase, DNA methyltransferase 1 (DNMT-1), has been shown in carcinomas of the colon, lung, liver, and prostate. Based on the nearly ubiquitous alterations of both DNA methylation and the retinoblastoma protein (pRb) pathway found in human cancer, we investigated a potential regulatory pathway linking the two alterations in murine and human prostate epithelial cells. Analysis of DNA methyltransferase levels in Rb-/- murine prostate epithelial cell lines revealed elevated Dnmt-1 levels. Genomic DNA sequence analysis identified conserved E2F consensus binding sites in proximity to the transcription initiation points of murine and human Dnmt-1. Furthermore, the Dnmt-1 promoter was shown to be regulated by the pRb/E2F pathway in murine and human cell lines of epithelial and fibroblast origin. In the absence of pRb, Dnmt-1 transcripts exhibited aberrant cell cycle regulation and Rb-/- cells showed aberrant methylation of the paternally expressed gene 3 (Peg3) tumor suppressor gene. These findings show a link between inactivation of the pRb pathway and induction of DNA hypermethylation of CpG island-containing genes in tumorigenesis.
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PMID:Regulation of DNA methyltransferase 1 by the pRb/E2F1 pathway. 1586 57

Expression of SHP-1 phosphatase, a key negative regulator of cell signaling, is lost in T cell lymphomas and other malignancies due to DNA methylation of the SHP-1 promoter by a currently undefined mechanism. We demonstrate that malignant T cells express DNA methyltransferase (DNMT) 1 and that constantly activated signal transducer and activator of transcription (STAT) 3 is capable of binding in vitro to DNA oligonucleotides corresponding to four STAT3 SIE/GAS binding sites identified in the SHP-1 promoter. STAT3, DNMT1, and histone deacetylase 1 form complexes and bind to the SHP-1 promoter in vivo. Treatment with pharmacologic grade DNMT1 anti-sense oligonucleotides and STAT3 small-interfering RNA induces in the malignant T cells DNA demethylation and expression of SHP-1 gene. These data indicate that STAT3 may, in part, transform cells by inducing epigenetic silencing of SHP-1 in cooperation with DNMT1 and, apparently, histone deacetylase 1. Reversal of such gene silencing represents an attractive aim for novel anticancer therapies.
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PMID:STAT3- and DNA methyltransferase 1-mediated epigenetic silencing of SHP-1 tyrosine phosphatase tumor suppressor gene in malignant T lymphocytes. 1587 Jan 98


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