title: Construction and characterization of a potent HIV-2 Tat transdominant mutant protein.
abstract: The human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2) Tat proteins Tat-1 and Tat-2 stimulate transcription of the viral long terminal repeat (LTR) sequences and are required for efficient viral replication. A class of mutant Tat proteins, termed "transdominant mutants," has been described that possesses relatively low transactivation activity, yet is able to inhibit the function of wild-type Tat. These mutant proteins contain a nonfunctional TAR RNA-binding domain but apparently retain a functional activation domain. A potential limitation for therapeutic use of transdominant mutants described to date is their low but significant basal level of transactivation for the HIV-1 or HIV-2 LTRs. In order to make an improved transdominant mutant, we have constructed Tat-2 proteins that contain mutations in four contiguous arginines at residues 81 to 84 in the RNA-binding domain. Using purified proteins and in vitro RNA-binding assays, we verified that these mutant Tat-2 proteins are defective for TAR RNA binding. We also verified that these mutant Tat-2 proteins bind to a cellular protein kinase in vitro that we have previously shown to bind specifically to the Tat-1 and Tat-2 activation domain. Using plasmid cotransfection assays, we compared the phenotypes of these mutant Tat-2 proteins with the most potent Tat-1 transdominant mutant described to date. One Tat-2 mutant, named "R81-84A," was found to be equivalent to the Tat-1 mutant in ability to inhibit wild-type Tat transactivation of HIV-1 and HIV-2 LTRs. Moreover, the R81-84A mutant possessed a significantly lower basal level of transactivation than the Tat-1 mutant. The R81-84A Tat-2 mutant is therefore a promising reagent for future development as an anti-HIV agent. Additionally, our results suggest that wild-type Tat-2 transactivation of the HIV-2 LTR is especially sensitive to inhibition by transdominant mutants.
authors.affiliation: Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030.
authors.forename: C O
authors.initials: CO
authors.lastname: Echetebu
authors.forename: H
authors.initials: H
authors.lastname: Rhim
authors.forename: C H
authors.initials: CH
authors.lastname: Herrmann
authors.forename: A P
authors.initials: AP
authors.lastname: Rice
mesh_terms: D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry; D002460:Cell Line; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000737:chemistry / Q000235:genetics*; D015756:Genes, tat; D015498:HIV-2 / Q000737:chemistry / Q000235:genetics*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism; D012367:RNA, Viral / Q000737:chemistry / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D014162:Transfection; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D015696:Gene Products, tat; D012367:RNA, Viral; D054322:tat Gene Products, Human Immunodeficiency Virus; D001120:Arginine; D011494:Protein Kinases