title: A novel transcription mechanism activated by ethanol: induction of Slc7a11 gene expression via inhibition of the DNA-binding activity of transcriptional repressor octamer-binding transcription factor 1 (OCT-1).
abstract: Solute carrier family 7, member 11 (Slc7a11) is a plasma membrane cystine/glutamate exchanger that provides intracellular cystine to produce glutathione, a major cellular antioxidant. Oxidative and endoplasmic reticulum stresses up-regulate Slc7a11 expression by activation of nuclear factor erythroid 2-related factor 2 and transcription factor 4. This study examined the effect of ethanol on Slc7a11 expression and the underlying mechanism involved. Treatment of mouse hepatic stellate cells with ethanol significantly increased Slc7a11 mRNA and protein levels. Deletion of a 20-bp DNA sequence between -2044 to -2024 upstream of the transcription start site significantly increased basal activity and completely abolished the ethanol-induced activity of the Slc7a11 promoter. This deletion did not affect Slc7a11 promoter activity induced by oxidative or endoplasmic reticulum stress. DNA sequence analysis revealed a binding motif for octamer-binding transcription factor 1 (OCT-1) in the deleted fragment. Mutation of this OCT-1 binding motif resulted in a similar effect as the deletion experiment, i.e. it increased the basal promoter activity and abolished the response to ethanol. Ethanol exposure significantly inhibited OCT-1 binding to the Slc7a11 promoter region, although it did not alter OCT-1 mRNA and protein levels. OCT-1 reportedly functions as either a transcriptional enhancer or repressor, depending on the target genes. Results from this study suggest that OCT-1 functions as a repressor on the Slc7a11 promoter and that ethanol inhibits OCT-1 binding to the Slc7a11 promoter, thereby increasing Slc7a11 expression. Taken together, inhibition of the DNA binding activity of transcriptional repressor OCT-1 is a mechanism by which ethanol up-regulates Slc711 expression.
authors.affiliation: Department of Physiology, Meharry Medical College, Nashville, Tennessee 37208, USA.
authors.forename: Xinghua
authors.initials: X
authors.lastname: Lin
authors.forename: Hong
authors.initials: H
authors.lastname: Yang
authors.forename: Hongfeng
authors.initials: H
authors.lastname: Zhang
authors.forename: LiChun
authors.initials: L
authors.lastname: Zhou
authors.forename: ZhongMao
authors.initials: Z
authors.lastname: Guo
mesh_terms: D020816:Amino Acid Motifs; D027182:Amino Acid Transport System y+ / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000235:genetics; D000431:Ethanol / Q000494:pharmacology*; D055166:Hepatic Stellate Cells / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D050811:Octamer Transcription Factor-1 / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements; D017384:Sequence Deletion; D015854:Up-Regulation / Q000187:drug effects* / Q000235:genetics
chemical_list: D027182:Amino Acid Transport System y+; D002492:Central Nervous System Depressants; D050811:Octamer Transcription Factor-1; C494166:Pou2f1 protein, mouse; D012333:RNA, Messenger; D012097:Repressor Proteins; C492255:Slc7a11 protein, mouse; D000431:Ethanol
keywords: Alcohol; Hepatic Stellate Cells; Mouse; Octamer-binding Transcription Factor 1; Solute Carrier Family 7, Member 11; Transcription Factors; Transporters