title: A fourth Sp1 site in the human immunodeficiency virus type 1 long terminal repeat is essential for negative-sense transcription.
abstract: We report the discovery of a fourth Sp1 binding site at the 5' end of the U3 region of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (HIV-1 Sp1 IV), localized to HXB2 nucleotides -433 to -441. This site is shown to bind Sp1 protein specifically in electrophoretic mobility shift assays. Sp1 protein appears to bind to HIV-1 Spl IV with 5 to 10 times lower affinity than to a consensus Sp1 site. Mutation of HIV-1 Sp1 IV in an HXB2-derived long terminal repeat-chloramphenicol acetyltransferase reporter construct gave no significant change in positive-sense transcription but abolished both basal and phorbol myristate acetate-activated negative-sense transcription. Taken together, the results further define the HIV-1 negative-sense promoter as an Sp1-dependent, phorbol myristate acetate-responsive, and Tat-inhibited promoter initiating at HXB2 nucleotide -450.
authors.affiliation: National Centre for HIV Virology Research, The Macfarlane Burnet Centre for Medical Research, Fairfield, Victoria, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Peeters
authors.forename: P F
authors.initials: PF
authors.lastname: Lambert
authors.forename: N J
authors.initials: NJ
authors.lastname: Deacon
mesh_terms: D016375:Antisense Elements (Genetics); D016325:HIV Long Terminal Repeat / Q000235:genetics*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D009154:Mutation; D011401:Promoter Regions, Genetic; D017421:Sequence Analysis; D014158:Transcription, Genetic
chemical_list: D016375:Antisense Elements (Genetics)