title: δEF1 associates with DNMT1 and maintains DNA methylation of the E-cadherin promoter in breast cancer cells.
abstract: Abnormal DNA methylation at the C-5 position of cytosine (5mC) of CpG dinucleotides is a well-known epigenetic feature of cancer. Levels of E-cadherin, which is regularly expressed in epithelial tissues, are frequently reduced in epithelial tumors due to transcriptional repression, sometimes accompanied by hypermethylation of the promoter region. δEF1 family proteins (δEF1/ZEB1 and SIP1/ZEB2), key regulators of the epithelial-mesenchymal transition (EMT), suppress E-cadherin expression at the transcriptional level. We recently showed that levels of mRNAs encoding δEF1 proteins are regulated reciprocally with E-cadherin level in breast cancer cells. Here, we examined the mechanism underlying downregulation of E-cadherin expression in three basal-type breast cancer cells in which the E-cadherin promoter region is hypermethylated (Hs578T) or moderately methylated (BT549 and MDA-MB-231). Regardless of methylation status, treatment with 5-aza-2'-deoxycytidine (5-aza), which inhibits DNA methyltransferases, had no effect on E-cadherin expression. Knockdown of δEF1 and SIP1 resulted in recovery of E-cadherin expression in cells lacking hypermethylation, whereas combined treatment with 5-aza synergistically restored E-cadherin expression, especially when the E-cadherin promoter was hypermethylated. Moreover, δEF1 interacted with DNA methyltransferase 1 (DNMT1) through the Smad-binding domain. Sustained knockdown of δEF1 family proteins reduced the number of 5mC sites in the E-cadherin promoter region, suggesting that these proteins maintain 5mC through interaction with DNMT1 in breast cancer cells. Thus, δEF1 family proteins appear to repress expression of E-cadherin during cancer progression, both directly at the transcriptional level and indirectly at the epigenetic level.
authors.affiliation: Department of Biochemistry, University of Yamanashi Yamanashi, Yamanashi, Chuo, 409-3898, Japan; Research Training Program for Undergraduates, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi Yamanashi, Yamanashi, Chuo, 409-3898, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Fukagawa
authors.forename: Hiroki
authors.initials: H
authors.lastname: Ishii
authors.forename: Keiji
authors.initials: K
authors.lastname: Miyazawa
authors.forename: Masao
authors.initials: M
authors.lastname: Saitoh
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism*; D015820:Cadherins / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D018899:CpG Islands; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism*; D019175:DNA Methylation; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000071799:Zinc Finger E-box-Binding Homeobox 1
chemical_list: D015820:Cadherins; C108381:GEMIN2 protein, human; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D014157:Transcription Factors; C486307:ZEB1 protein, human; D000071799:Zinc Finger E-box-Binding Homeobox 1; D000076123:DNA (Cytosine-5-)-Methyltransferase 1; D004248:DNA (Cytosine-5-)-Methyltransferases; C000619380:DNMT1 protein, human
keywords: Cancer cells; DNA methylation; E-cadherin; EMT; δEF1