title: Targeting tat inhibitors in the assembly of human immunodeficiency virus type 1 transcription complexes.
abstract: Human immunodeficiency virus type 1 (HIV-1) transcription is regulated by the viral Tat protein, which relieves a block to elongation by recruiting an elongation factor, P-TEFb, to the viral promoter. Here, we report the discovery of potent Tat inhibitors that utilize a localization signal to target a dominant negative protein to its site of action. Fusing the Tat activation domain to some splicing factors, particularly to the Arg-Ser (RS) domain of U2AF65, creates Tat inhibitors that localize to subnuclear speckles, sites where pre-mRNA processing factors are stored for assembly into transcription complexes. A U2AF65 fusion named T-RS interacts with the nonphosphorylated C-terminal domain of RNA polymerase II (RNAP II) via its RS domain and is loaded into RNAP II holoenzyme complexes. T-RS is recruited efficiently to the HIV-1 promoter in a TAR-independent manner before RNAP II hyperphosphorylation but not to cellular promoters. The "preloading" of T-RS into HIV-1 preinitiation complexes prevents the entry of active Tat molecules, leaving the complexes in an elongation-incompetent state and effectively suppressing HIV-1 replication. The ability to deliver inhibitors to transcription complexes through the use of targeting/localization signals may provide new avenues for designing viral and transcription inhibitors.
authors.affiliation: Department of Biochemistry and Biophysics, University of California-San Francisco, 600 16th St., San Francisco, CA 94143-2280, USA.
authors.forename: Iván
authors.initials: I
authors.lastname: D'Orso
authors.forename: Jocelyn R
authors.initials: JR
authors.lastname: Grunwell
authors.forename: Robert L
authors.initials: RL
authors.lastname: Nakamura
authors.forename: Chandreyee
authors.initials: C
authors.lastname: Das
authors.forename: Alan D
authors.initials: AD
authors.lastname: Frankel
mesh_terms: D000595:Amino Acid Sequence; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015497:HIV-1 / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000378:metabolism / Q000821:virology; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: D015696:Gene Products, tat