title: HIV Tat represses transcription through Sp1-like elements in the basal promoter.
abstract: MHC class I genes are potently repressed by HIV Tat, which transactivates the HIV LTR. Tat represses class I transcription by binding to complexes associated with a novel promoter element, consisting of Sp1-like DNA binding sites. Transcription by other Sp1-dependent promoters, such as MDR1 and the minimal SV40 promoters, is also repressed by Tat, whereas the human beta-actin promoter is neither activated by Sp1 nor repressed by Tat. Tat repression can be overcome by a strong enhancer element. Thus, the SV40 72 bp enhancer element confers protection from Tat-mediated repression on both the minimal SV40 promoter and the class I promoter. Surprisingly, Tat can activate the class I promoter in the presence of both the HIV TAR element and a strong upstream enhancer. These data demonstrate that Tat differentially affects Sp1-responsive promoters, depending on promoter architecture.
authors.affiliation: Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Howcroft
authors.forename: L A
authors.initials: LA
authors.lastname: Palmer
authors.forename: J
authors.initials: J
authors.lastname: Brown
authors.forename: B
authors.initials: B
authors.lastname: Rellahan
authors.forename: F
authors.initials: F
authors.lastname: Kashanchi
authors.forename: J N
authors.initials: JN
authors.lastname: Brady
authors.forename: D S
authors.initials: DS
authors.lastname: Singer
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000235:genetics; D005786:Gene Expression Regulation; D015696:Gene Products, tat / Q000235:genetics*; D006367:HeLa Cells; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D017354:Point Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics; D015533:Transcriptional Activation
chemical_list: D015696:Gene Products, tat; D015395:Histocompatibility Antigens Class I; D004247:DNA