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)

Previous studies suggest that estrogen receptor-positive (ER+) breast cancer cells acquire resistance to transforming growth factor-beta (TGF-beta) because of reduced expression levels of TGF-beta receptor type II (RII). We now report that treatment of ER+ breast cancer cells with the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-2'-dC) leads to accumulation of RII transcript and protein in three different cell lines. RII induction restored TGF-beta response in MCF-7L breast cancer cells as indicated by the enhanced activity of a TGF-beta responsive promoter-reporter construct (p3TP-Lux). A transiently transfected RII promoter-reporter element (RII-chloramphenicol acetyltransferase) showed an increase in activity in the 5-aza-2'-dC-treated MCF-7L cells compared with untreated cells, suggesting the activation of a transactivator of RII transcription. Using electrophoretic mobility shift assays, the enhanced binding of proteins from 5-aza-2'-dC-treated MCF-7L nuclear extracts to radiolabeled Sp1 oligonucleotides was demonstrated. An RII promoter-chloramphenicol acetyltransferase construct containing a mutation in the Sp1 site was not expressed in the 5-aza-2'-dC-treated MCF-7L cells, further demonstrating that induction of Sp1 activity by 5-aza-2'-dC in the MCF-7L cells was critical to RII expression. Northern analysis indicated that 5-aza-2'-dC treatment did not affect the Sp1 transcript levels. Western blot analysis revealed an increase of Sp1 protein in the 5-aza-2'-dC-treated MCF-7L cells, but there was no change in the c-Jun levels. Studies after cyclohexamide treatment suggested an increase in the Sp1 protein stability from the 5-aza-2'-dC-treated MCF-7L extracts compared with untreated control extracts. These results indicate that the transcriptional repression of RII in the ER+ breast cancer cells is caused by suboptimal activity of Sp1, whereas treatment with 5-aza-2'-dC stabilizes the protein thus increasing steady-state Sp1 levels and thereby leads to enhanced RII transcription and subsequent restoration of TGF-beta sensitivity.
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PMID:Induction of transforming growth factor-beta receptor type II expression in estrogen receptor-positive breast cancer cells through SP1 activation by 5-aza-2'-deoxycytidine. 963 22

In this report, we describe the mechanism of TGF-beta receptor type I (RI) repression in the GEO human colon carcinoma cells. Treatment of GEO cells with the DNA methyltransferase inhibitor, 5 azacytidine induced RI expression and restored TGF-beta response. A stably transfected RI promoter-reporter construct (RI-Luc) expressed higher activity in the 5 aza C treated GEO cells, suggesting the activation of a transactivator for RI transcription. Gel shift analysis indicated enhanced binding of proteins from the 5 aza C treated nuclear extracts to radiolabeled Sp1 oligonucleotides specifically contained in the RI promoter. Protein stability studies after cyclohexamide treatment suggested an increase in the Sp1 protein stability from the 5 aza C treated GEO cells. Further, transfection of Sp1 cDNA into untreated GEO control cells increased RI promoter activity and thus induced RI expression. 5 aza C mediated Sp1 expression in Sp1 deficient GEO colon and MCF-7 breast cancer cells also enhanced the activity of several other Sp1 dependent promoters such as TGF-beta receptor type II (RII), Cyclin A and p21/waf1/cip1. These results indicate that restoration of Sp1 in several different types of Sp1 deficient cells leads to enhanced activation of a wide range of Sp1 dependent promoters.
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PMID:Repression of transforming growth factor-beta receptor type I promoter expression by Sp1 deficiency. 1103 Jan 55

Bortezomib reversibly inhibits 26S proteasomal degradation, interferes with NF-kappaB, and exhibits antitumor activity in human malignancies. Zinc finger protein Sp1 transactivates DNMT1 gene in mice and is functionally regulated through protein abundance, posttranslational modifications (ie, ubiquitination), or interaction with other transcription factors (ie, NF-kappaB). We hypothesize that inhibition of proteasomal degradation and Sp1/NF-kappaB-mediated transactivation may impair aberrant DNA methyltransferase activity. We show here that, in addition to inducing accumulation of polyubiquitinated proteins and abolishment of NF-kappaB activities, bortezomib decreases Sp1 protein levels, disrupts the physical interaction of Sp1/NF-kappaB, and prevents binding of the Sp1/NF-kappaB complex to the DNMT1 gene promoter. Abrogation of Sp1/NF-kappaB complex by bortezomib causes transcriptional repression of DNMT1 gene and down-regulation of DNMT1 protein, which in turn induces global DNA hypomethylation in vitro and in vivo and re-expression of epigenetically silenced genes in human cancer cells. The involvement of Sp1/NF-kappaB in DNMT1 regulation is further demonstrated by the observation that Sp1 knockdown using mithramycin A or shRNA decreases DNMT1 protein levels, which instead are increased by Sp1 or NF-kappaB overexpression. Our results unveil the Sp1/NF-kappaB pathway as a modulator of DNA methyltransferase activity in human cancer and identify bortezomib as a novel epigenetic-targeting drug.
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PMID:Bortezomib induces DNA hypomethylation and silenced gene transcription by interfering with Sp1/NF-kappaB-dependent DNA methyltransferase activity in acute myeloid leukemia. 1808 45