Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.1.1.37 (DNA methyltransferase)
 4,983 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Epstein-Barr Virus (EBV) latency C promoter (Cp) is the origin of transcripts for six viral proteins. The promoter is active in lymphoblastoid B-cell lines but silent in many EBV-associated tumors and tumor cell lines. In these latter cell lines, the viral episome is hypermethylated in the vicinity of this promoter. We show that in such a cell line (Rael, a Burkitt's lymphoma line), 5-azacytidine inhibits DNA methyltransferase, brings about demethylation of EBV genomes, activates Cp transcription, and induces the expression of EBNA-2. Investigation of the phenomenon demonstrates the importance of the methylation status of a particular CpG site for the regulation of the Cp: (i) genomic sequencing shows that this site is methylated when the Cp is inactive and is not methylated when the promoter is active; (ii) methylation or transition mutation at this site abolishes complex formation with a cellular binding activity (CBF2) as determined by electrophoretic mobility shift analyses, competition binding analyses, and DNase I footprinting; and (iii) a single C --> T transition mutation at this site is associated with a marked reduction (> 50-fold) of transcriptional activity in a reporter plasmid. Thus, the CBF2 binding activity is shown to be methylation sensitive and crucial to EBNA-2-mediated activation of the Cp.
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PMID:Transcriptional activation of the Epstein-Barr virus latency C promoter after 5-azacytidine treatment: evidence that demethylation at a single CpG site is crucial. 756 67

We analyzed the methylation patterns of CpG dinucleotides in the regulatory region of the latent Epstein-Barrvirus (EBV) promoter BCR2 (also called C promoter, Cp) using automated fluorescent genomic sequencing after bisulfite-induced modification of DNA. BCR2 is one of the alternative promoters for transcripts encoding the growth-transformation-associated nuclear antigens EBNA 1-6 which are expressed in a host cell phenotype dependent manner. Well characterized clones isolated from the Burkitt's lymphoma (BL) line Mutu differing from each other as to their phenotype and EBV latent gene expression were used in the present study. We found that in Mutu BL III clone 99 which is actively using the BCR2 promoter the regulatory sequences are unmethylated with two exceptions (position 10702 and 10799). In contrast, there are 15 methylated cytosines in the same region in Mutu BL I clone 216 where the BCR2 promoter is silent. Cytosines which are potential targets of DNA methyltransferase in the immediate vicinity or within the attachment sites of cellular C promoter binding factors CBF1 and CBF2 remained hypomethylated in Mutu BL I clone 216. This suggests a role for a hypermethylated region (nucleotides 10666 -10865, -639 to -440 bases upstream from the beginning of the TATA box at position 11305) in silencing of the BCR2 promoter in these cells.
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PMID:Analysis of methylation patterns in the regulatory region of the latent Epstein-Barr virus promoter BCR2 by automated fluorescent genomic sequencing. 962 32

As an important regulator in Wnt-signaling pathway, the APC gene is involved in apoptosis and cell cycle arrest. The loss of APC function is observed in most familial adenomatous polyposis-associated and sporadic colorectal cancer. APC gene is frequently inactivated by DNA mutations. However, hypermethylation in APC gene promoter was also observed in different cancers. In this study, by analyzing the methylation status of APC promoter in 22 colorectal cancer cell lines with different APC expression levels, we identified Regions A and B in the promoter, where the methylation of CpG sites was invariably correlated with the loss of gene expression. By nuclease accessibility assay, we also observed a correlation between the closed chromatin conformation in APC promoter and loss of gene expression. When the nonexpressing cell lines were treated with a DNA methyltransferase inhibitor, 5-Aza-2'-Deoxycytidine, the APC expression in these cells was induced, CpG sites were demethylated, and closed chromatin conformation was opened. However, when these cell lines were treated with a histone deacetylase inhibitor, Trichostatin A, no significant changes in APC expression, methylation status, and chromatin conformation were observed. Using transient transfection assay, a CCAAT box located in Region B was identified, which was involved in up-regulation of APC expression. Methylation of CpG sites around the CCAAT box resulted in a significant inhibition in the gene expression. The specific binding of a transcription factor CCAAT-binding factor (CBF) to the CCAAT box was determined by electrophoretic mobility shift analysis. The binding was inhibited after CpG sites close to the CCAAT box were methylated, indicating that DNA methylation can silence gene expression through interfering with the binding of transcription factors to the promoter. The biological function of CBF in APC gene regulation was further indicated by the decrease of luciferase activities in cells cotransfected with a plasmid carrying APC promoter/luciferase gene and a plasmid expressing dominant negative CBF mutant. In summary, methylation of CpG sites around CCAAT box in APC promoter inhibits the gene expression by changing the chromatin conformation and interfering with the binding of transcription factor CBF to CCAAT box.
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PMID:Promoter methylation inhibits APC gene expression by causing changes in chromatin conformation and interfering with the binding of transcription factor CCAAT-binding factor. 1508 81