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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Realization that many tumor suppressor genes are silenced by epigenetic mechanisms has stimulated the discovery of novel tumor suppressor genes. We used a variety of research tools to search for genes that are epigenetically silenced in human endometrial cancers. Changes in global gene expression of the endometrial cancer cell line Ishikawa was analyzed after treatment with the demethylating agent 5-aza-2'-deoxycytidine combined with the histone deacetylase inhibitor suberoylanilide bishydroxamide. By screening over 22,000 genes, candidate tumor suppressor genes were identified. Additional microarray analysis and real-time reverse transcription-PCR of normal and cancerous endometrial samples and search for CpG islands further refined the list. Tazarotene-induced gene-1 (Tig1) and CCAAT/enhancer binding protein-alpha (C/ebpalpha) were chosen for further study. Expression of both genes was low in endometrial cancer cell lines and clinical samples but high in normal endometrial tissues. Bisulfite sequencing, restriction analysis, and/or methylation-specific PCR revealed aberrant methylation of the CpG island in the Tig1 gene of all 6 endometrial cancer cell lines examined and 4 of 18 clinical endometrial cancers, whereas the C/ebpalpha promoter remained unmethylated in endometrial cancers. Chromatin immunoprecipitation showed increased acetylated histone H3 bound to both Tig1 and C/ebpalpha genes after treatment with 5-aza-2'-deoxycytidine and/or suberoylanilide bishydroxamide. Forced expression of either TIG1 or C/EBPalpha led to significant growth reduction of Ishikawa cells. Our data suggest that C/ebpalpha and Tig1 function as tumor suppressor proteins in endometrial cancers and that their reexpression may be a therapeutic target.
Mol Cancer Res 2005 May
PMID:Discovery of epigenetically masked tumor suppressor genes in endometrial cancer. 1588 97

We investigated the CpG methylation of 19 specific members of Alu sub-families in human DNA isolated from whole blood, using an assay based on methylation-sensitive restriction endonuclease digestion of genomic DNA and 'hot-stop' polymerase chain reaction. We found significant interindividual variability in the level of methylation for specific Alu elements among the members of 48 three-generation families. Surprisingly, some of the elements also displayed quantitative parent of origin methylation differences; i.e. the mean level of methylation differed significantly when the insertions were transmitted through paternal versus maternal meiosis. Bisulfite sequence analysis of individual elements at such loci suggests, further, that maternal and paternal elements differ in the propensity of particular CpG sites to become unmethylated. Some individuals who exhibited high levels of methylation at specific Alu elements came from families in which more than one member also exhibited abnormal patterns of methylation at the differentially methylated regions of the IGF2/H19 or IGF2R loci, suggesting that there may be heritable differences between individuals in the fidelity with which allelic DNA methylation differences are established or maintained. Quantitative parental origin differences in methylation were identified only for Alu elements that lie in sub-telomeric or sub-centromeric bands of human chromosomes, whereas those assayed at intermediate positions did not exhibit any significant differences. The centromere/telomere restricted location of the methylation differences and the fact that none of these differences occur in regions of chromosomes known to contain transcriptionally imprinted genes suggest that maternal/paternal epigenetic modifications may play additional roles in processes other than transcriptional control.
Hum Mol Genet 2005 Aug 01
PMID:Interindividual variability and parent of origin DNA methylation differences at specific human Alu elements. 1597 27

The baboon is a suitable and relevant animal model to study the mechanism of human globin gene switching. This investigation addresses the role of DNA methylation and histone coding in globin gene switching in the baboon, Papio anubis. Bisulfite sequencing and chromatin immunoprecipitation studies were performed in erythroid cells purified from fetuses of varying gestational ages and from adult bone marrow to analyze the manner that changes in DNA methylation of the epsilon-, gamma-, and beta-globin promoters and association of ac-H3, ac-H4, H3-dimeK4, H3-dimeK36, and H3-dimeK79 with the epsilon-, gamma-, and beta-globin promoters occur during development. Changes in DNA methylation of the epsilon- and gamma-globin gene promoters during transitional stages of globin gene switching were consistent with the stochastic model of methylation and a role of DNA methylation in gene silencing. Enrichment of ac-H3, ac-H4, and pol II at the promoters of developmentally active genes was observed, while the pattern of distribution of H3-dimeK4 and H3-dimeK79 suggests that these modifications are found near both currently and formerly active promoters. Enrichment of H3-dimeK36 at the silenced epsilon-globin gene promoter was observed. These studies demonstrate that coordinated epigenetic modifications in the chromatin structure of the beta-like globin gene promoters accompany the highly regulated changes in expression patterns of these genes during development.
Blood Cells Mol Dis
PMID:Developmental changes in DNA methylation and covalent histone modifications of chromatin associated with the epsilon-, gamma-, and beta-globin gene promoters in Papio anubis. 1652

In this study, we have isolated by affinity chromatography, using anti-m5C antibody as a ligand, a DNA encoding reverse transcriptase of LINE retrotransposon (RT LINE) in both Entamoeba invadens and Entamoeba histolytica. RT LINE transcripts were detected in E. histolytica but were absent from E. invadens. The methylation status of genomic copies of E. invadens RT LINE was confirmed by bisulfite analysis. In contrast, all the genomic copies of the E. histolytica RT LINE analyzed in this study were not methylated. Many of these genomic copies diverge from the RT LINE isolated by m5C affinity chromatography by a number of mutations that includes conversion of C to T and G to A. These mutations are reminiscent of the conversion of C to T (and G to A on the complementary DNA strand) that occurred during primate evolution in Alu elements following accelerated deamination of methylated cytosines. E. invadens and E. histolytica RT LINEs isolated by affinity chromatography were cloned in a pEhAct Neo vector, amplified in E. coli GM2163 (dam-dcm) and transformed into E. histolytica. Bisulfite analysis of transfected amoeba showed the presence of m5C in E. invadens RT LINE replicated in E. histolytica, but not in E. histolytica RT LINE or in the neomycine phosphotransferase gene, which is also carried by the pEhAct Neo vector. These results suggest the existence of a specific mechanism based on DNA methylation that controls retrotransposons in these parasites.
Mol Biochem Parasitol 2006 May
PMID:DNA methylation and targeting of LINE retrotransposons in Entamoeba histolytica and Entamoeba invadens. 1653 Feb 79

Assays to measure DNA methylation, which are important in epigenetic research and clinical diagnostics, typically rely on conversion of unmethylated cytosine to uracil by sodium bisulfite. However, no study has comprehensively evaluated the precision and performance characteristics of sodium bisulfite conversion and subsequent quantitative methylation assay. We developed quantitative real-time polymerase chain reaction (MethyLight) to measure percentage of methylated reference (PMR, ie, degree of methylation) for the MGMT, MLH1, and CDKN2A (p16) promoters. To measure the precision of bisulfite conversion, we bisulfite-treated seven different aliquots of DNA from each of four paraffin-embedded colon cancer samples. To assess run-to-run variation, we repeated MethyLight five times. Bisulfite-to-bisulfite coefficient of variation (CV) of PMR ranged from 0.10 to 0.38 (mean, 0.21), and run-to-run CV of PMR ranged from 0.046 to 0.60 (mean, 0.31). Interclass correlation coefficients were 0.74 to 0.84 for the three loci, indicating good reproducibility. DNA mixing study with methylated and unmethylated DNA showed good linearity of the assay. Of 272 colorectal cancers evaluated, most showed PMR either <1 or >10, and promoter methylation (PMR >4) was tightly associated with loss of respective protein expression (P < 10(-16)). In conclusion, sodium bisulfite conversion and quantitative MethyLight assays have good precision and linearity and can be effectively used for high-throughput DNA methylation analysis on paraffin-embedded tissue.
J Mol Diagn 2006 May
PMID:Precision and performance characteristics of bisulfite conversion and real-time PCR (MethyLight) for quantitative DNA methylation analysis. 1664

DNA methylation can be analyzed easily by qualitative or quantitative polymerase chain reaction (PCR)-based methods, including methylation-specific PCR (MSP), bisulfite sequencing, methylation-sensitive restriction enzyme PCR, combined bisulfite restriction analysis (COBRA), methylation-sensitive single nucleotide primer extension (Ms-SNuPE), and quantitative real-time MSP. MSP, which couples the bisulfite modification of DNA and PCR, is fast, highly sensitive, specific, and widely applied for DNA methylation analyses. Bisulfite modification converts unmethylated cytosine to uracil, whereas methylcytosine remains unmodified. Most of these methods require specific PCR primers that are designed to distinguish between methylated and unmethylated DNA sequences. Bisulfite sequencing is comparatively time-consuming. Methylation-sensitive restriction enzyme PCR combines methylation-sensitive restriction enzyme digestion and PCR. After enzyme digestion, PCR products are obtained if the enzyme does not digest the methylated CpG sites within the specified DNA region. COBRA, Ms-SNuPE, and quantitative real-time MSP allow the quantitative analyses of DNA methylation.
Methods Mol Biol 2006
PMID:Qualitative and quantitative polymerase chain reaction-based methods for DNA methylation analyses. 1691 51

The BubR1 mitotic-checkpoint protein monitors proper attachment of microtubules to kinetochores, and links regulation of chromosome-spindle attachment to mitotic-checkpoint signaling. Thus, disruption of BubR1 activity results in a loss of checkpoint control, chromosomal instability caused by a premature anaphase, and/or the early onset of tumorigenesis. The mechanisms by which deregulation and/or abnormalities of BubR1 expression operate, however, remain to be elucidated. In this study, we demonstrate that levels of BubR1 expression are significantly increased by demethylation. Bisulfite sequencing analysis revealed that the methylation status of two CpG sites in the essential BubR1 promoter appear to be associated with BubR1 expression levels. Associations of MBD2 and HDAC1 with the BubR1 promoter were significantly relieved by addition of 5-aza-2'-deoxycytidine, an irreversible DNA methyltransferase inhibitor. However, genomic DNA isolated from 31 patients with colorectal carcinomas exhibited a +84A/G polymorphic change in approximately 60% of patients, but this polymorphism had no effect on promoter activity. Our findings indicate that differential regulation of BubR1 expression is associated with changes in BubR1 promoter hypermethylation patterns, but not with promoter polymorphisms, thus providing a novel insight into the molecular regulation of BubR1 expression in human cancer cells.
Exp Mol Med 2007 Apr 30
PMID:Differential promoter methylation may be a key molecular mechanism in regulating BubR1 expression in cancer cells. 1746 81

The Hedgehog/Patched signaling pathway plays a prominent role during mammalian development but it is also involved in oncogenic transformation. We investigated the methylation status of the Patched promotor in a set of basocellular carcinomas of the skin and ovarian tumors as an alternative to mutational causes of the pathway deregulation. Our aim was to define a possible role of genetic and/or epigenetic mechanisms of Hedgehog/Patched signal transduction in the development of these tumors. Bisulfite-converted DNA from tumors and from matched healthy tissue was amplified by a specific PCR and the CpG-rich regions of the Patched promoter were sequenced. Two promoter regions showed statistically significant hypermethylation compared to healthy controls in ovarian tumors; more significantly in the region in the vicinity of Gli1-binding sites and less significantly in the region containing the ATG codon. But, in basocellular carcinomas of the skin we observed no difference in methylation, suggesting different mechanisms of neoplasia in these tumors.
Int J Mol Med 2007 Jun
PMID:The Patched gene is epigenetically regulated in ovarian dermoids and fibromas, but not in basocellular carcinomas. 1748 19

CST6 is a breast tumor suppressor gene that is expressed in normal breast epithelium, but is epigenetically silenced as a consequence of promoter hypermethylation in metastatic breast cancer cell lines. In the current study, we investigated the expression and methylation status of CST6 in primary breast tumors and lymph node metastases. 25/45 (56%) primary tumors and 17/20 (85%) lymph node metastases expressed significantly lower levels of cystatin M compared to normal breast tissue. Bisulfite sequencing demonstrated CST6 promoter hypermethylation in 11/23 (48%) neoplastic lesions analyzed, including 3/11 (27%) primary tumors and 8/12 (67%) lymph node metastases. In most cases (12/23, 52%), the expression of cystatin M directly reflected CST6 promoter methylation status. In remaining lesions (8/23, 35%) loss of cystatin M was not associated with CST6 promoter hypermethylation, indicating that other mechanisms can account for loss of CST6 expression. These results show that methylation-dependent silencing of CST6 occurs in a subset of primary breast cancers, but more frequently in metastatic lesions, possibly reflecting progression-related genomic events. To examine this possibility, primary breast tumors and matched lymph node metastases were analyzed. In 2/3 (67%) patients, primary tumors were positive for cystatin M and negative for CST6 promoter methylation, and matched metastatic lesions lacked cystatin M expression and CST6 was hypermethylated. This observation suggests that progression-related epigenetic alterations in CST6 gene expression can accompany metastatic spread from a primary tumor site. Overall, the results of the current investigation suggest that methylation-dependent epigenetic silencing of CST6 represents an important mechanism for loss of CST6 during breast tumorigenesis and/or progression to metastasis.
Exp Mol Pathol 2007 Oct
PMID:Methylation-dependent silencing of CST6 in primary human breast tumors and metastatic lesions. 1754 Mar 67

Two recent clinical trials have shown that the placenta growth factor (PlGF) is up-regulated after bevacizumab treatment in colorectal cancer and after SU11248 treatment in metastatic renal cell carcinoma. The regulation of expression for the vascular endothelial growth factor (VEGF) has been well documented in human tumors; however, the data for PlGF are lacking. We investigated the epigenetic regulation of PlGF and correlated the results with clinicopathologic features. We used plgf promoter analysis, cDNA microarray, immunohistochemistry, and Northern blot analysis to determine the expression level of PlGF in 22 human lung carcinoma and 11 colorectal tumors and in 12 cell lines. Sodium bisulfite modification of genomic DNA followed by methylation-specific PCR (MSP) and sequencing were used to determine the methylation status of the PlGF promoter. Treatments with 5-aza-2'-deoxycytidine and trichostatin A (TSA) were used to reactivate PlGF expression. Significance analysis showed that PlGF expression level was low in human lung and colorectal tumor tissues and in cell lines. PlGF gene promoter was hypermethylated. Treatment with the demethylating agent 5-Aza-dC restored PlGF transcript expression in the lung and colon carcinoma cell lines. By combining the results from cDNA microarray, immunohistochemistry, and MSP, we report, for the first time, that the PlGF gene promoter is methylated, and methylation may be one of the mechanisms that contributes to the low PlGF expression level in human lung and colorectal tumor tissues and cell lines.
Mol Cancer Res 2007 Sep
PMID:Down-regulation of placenta growth factor by promoter hypermethylation in human lung and colon carcinoma. 1770 40


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