title: Human immunodeficiency virus type-1 Tat is an integral component of the activated transcription-elongation complex.
abstract: The human immunodeficiency virus type 1 transactivator protein, Tat, stimulates transcriptional elongation from the viral long terminal repeat. To test whether Tat associates directly with activated transcription complexes, we have used the lac repressor protein (LacR) to "trap" elongating RNA polymerases. The arrested transcription complexes were purified by binding biotinylated templates to streptaviridin-coated magnetic beads. Transcription complexes were released from the magnetic beads following cleavage of the templates with restriction enzymes and were immunoblotted with antibodies to Tat, LacR and RNA polymerase II. The Tat protein copurified with RNA polymerase bound to wild-type templates but did not copurify with transcription complexes prepared by using templates carrying mutations in the transactivation response element (TAR) RNA. We conclude that Tat and cellular cofactors become attached to the transcription complex during its transit through TAR.
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom.
authors.forename: N J
authors.initials: NJ
authors.lastname: Keen
authors.forename: M J
authors.initials: MJ
authors.lastname: Gait
authors.forename: J
authors.initials: J
authors.lastname: Karn
mesh_terms: D001483:Base Sequence; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000378:metabolism*; D016325:HIV Long Terminal Repeat; D015497:HIV-1 / Q000235:genetics*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009875:Operator Regions, Genetic; D012320:RNA Polymerase III / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D054322:tat Gene Products, Human Immunodeficiency Virus; D000099253:Trans-Activation Responsive RNA-Binding Protein
chemical_list: D015696:Gene Products, tat; D046911:Macromolecular Substances; D012320:RNA Polymerase III; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D000099253:Trans-Activation Responsive RNA-Binding Protein