title: Gap junction Cx26 gene modulation by phorbol esters in benign and malignant human mammary cells.
abstract: Connexin (Cx) 26, a major gap junction protein expressed in mammary epithelial cells, has been considered to be a tumor suppressor gene candidate. This study investigated the molecular mechanism of transcriptional up-regulation of Cx26 by phorbol ester (TPA) in human immortalized MCF-10 mammary epithelial cells and MDA-MB-231 mammary cancer cells. Such up-regulation was mediated through the protein kinase C pathway and could be blocked by the PKC inhibitor, calphostin C. Based on the results of the nuclear run-on assay, there was a TPA-induced increase in the rate of transcriptional initiation. We identified a TPA-induced DNase I hypersensitivity (DH) region approximately 1 kb 5' upstream of the ATG translation starting site. Sequence analysis revealed that this DH region was located in intron 1 and contained two TRE-like TGAT/ATCA elements, two 5'TTCA3' motifs and a 5'AGGAAG3' PEA3 motif. Both TRE-like elements were capable of binding AP1. TPA inducibility of this DH region was seen by the CAT reporter assay and appeared to be direction-dependent suggesting a functional cooperation between PEA3/TTCA and TRE.
authors.affiliation: Breast Cancer Research Laboratory, Department of Medicine, University of Minnesota Medical School, Minneapolis, MN 55455, USA.
authors.forename: G Y
authors.initials: GY
authors.lastname: Li
authors.forename: H H
authors.initials: HH
authors.lastname: Lin
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Tu
authors.forename: D T
authors.initials: DT
authors.lastname: Kiang
mesh_terms: D001483:Base Sequence; D001940:Breast; D001943:Breast Neoplasms; D002461:Cell Line, Transformed; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D000072259:Connexin 26; D017630:Connexins / Q000096:biosynthesis* / Q000235:genetics*; D003850:Deoxyribonuclease I; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D017930:Genes, Reporter; D006801:Humans; D008969:Molecular Sequence Data; D009281:Naphthalenes / Q000494:pharmacology; D014176:Protein Biosynthesis; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012045:Regulatory Sequences, Nucleic Acid; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D017630:Connexins; D004791:Enzyme Inhibitors; C000607042:GJB2 protein, human; D009281:Naphthalenes; D011993:Recombinant Fusion Proteins; D000072259:Connexin 26; D015500:Chloramphenicol O-Acetyltransferase; D011493:Protein Kinase C; D003850:Deoxyribonuclease I; C058819:calphostin C; D013755:Tetradecanoylphorbol Acetate