title: The E-box motif in the proximal ABCA1 promoter mediates transcriptional repression of the ABCA1 gene.
abstract: To identify regulatory elements in the proximal human ATP-binding cassette transporter A1 (hABCA1) gene promoter we transfected RAW cells with plasmids containing mutations in the E-box, AP1, and liver X receptor (LXR) elements as well as the two Sp1 motifs. Point mutations in either Sp1 site or in the AP1 site had only a minor effect whereas mutation of the LXR element decreased promoter activity. In contrast, mutation or deletion of the E-box motif caused a 3-fold increase in transcriptional activity under basal conditions. Gel shift and DNaseI footprint analysis showed binding of a protein or protein complex to this region. Preincubation of nuclear extracts with antibodies established that USF1, USF2, and fos related antigen (Fra) 2 bind to DNA sequences in the human ABCA1 promoter that contains the intact E-box but not the mutant or deleted E-box. Co-transfection of USF1 and USF2 enhanced, but Fra2 repressed, ABCA1 promoter activity. Thus, a complex consisting of USF1, USF2, and Fra2 binds the E-box motif 147 bp upstream of the transcriptional start site and facilitates repression of the human ABCA1 promoter. These combined studies identify a novel site in the human ABCA1 promoter involved in the regulation of ABCA1 gene expression.
authors.affiliation: Molecular Disease Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1666, USA.
authors.forename: Xiao-Ping
authors.initials: XP
authors.lastname: Yang
authors.forename: Lita A
authors.initials: LA
authors.lastname: Freeman
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Knapper
authors.forename: Marcelo J A
authors.initials: MJ
authors.lastname: Amar
authors.forename: Alan
authors.initials: A
authors.lastname: Remaley
authors.forename: H Bryan
authors.initials: HB
authors.lastname: Brewer
authors.forename: Silvia
authors.initials: S
authors.lastname: Santamarina-Fojo
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology; D024721:E-Box Elements / Q000235:genetics*; D051921:Fos-Related Antigen-2; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D009154:Mutation; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology; D014158:Transcription, Genetic; D051720:Upstream Stimulatory Factors
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D004268:DNA-Binding Proteins; C497872:FOSL2 protein, human; D051921:Fos-Related Antigen-2; C497873:Fosl2 protein, mouse; D014157:Transcription Factors; C497181:USF1 protein, human; C497184:USF2 protein, human; D051720:Upstream Stimulatory Factors; C497183:Usf1 protein, mouse; C497186:Usf2 protein, mouse