Document 0591
 DOCN  M9550591
 TI    Distinct regions in human T-cell lymphotropic virus type I tax mediate
       interactions with activator protein CREB and basal transcription
       factors.
 DT    9505
 AU    Adya N; Giam CZ; Department of Medicine, Case Western Reserve
       University,; Cleveland, Ohio 44106.
 SO    J Virol. 1995 Mar;69(3):1834-41. Unique Identifier : AIDSLINE
       MED/95156616
 AB    Human T-cell lymphotropic virus type I (HTLV-I) transactivator Tax
       augments transcription from three (cyclic AMP response element
       (CRE)-containing 21-bp repeats in the viral long terminal repeat and
       several other cis regulatory elements, including the NF-kappa B binding
       sites and the serum response element. Tax does not bind DNA directly;
       rather, it acts via cellular sequence-specific DNA binding proteins to
       stimulate transcription. We have shown recently that Tax forms
       multiprotein complexes with the heterodimeric and homodimeric forms of a
       ubiquitous cellular transcription factor, CREB (CRE binding protein). In
       vitro selection for preferred Tax-CREB binding sites indicates that the
       Tax-CREB complex exhibits greatly increased DNA recognition specificity
       and assembles preferentially on CRE motifs, TGACGT/C, flanked by long
       runs of G (5') and/or C (3') residues, as found in the HTLV-I 21-bp
       repeats. The indirect tethering of Tax to the 21-bp repeats via CREB is
       crucial for Tax transactivation. We now report the domain organization
       of Tax by characterizing its mutants. Tax mutants with alterations in
       the NH2 terminus, including three deletion mutants, Tax(6-353),
       Tax(21-353), and Tax(89-353), and two amino acid substitution mutants,
       M1 (H3S) and M7 (C29A, P30S), all failed to interact with CREB in vitro.
       In contrast, a short COOH-terminal deletion, Tax(1-319), and a Tax
       mutant with amino acid substitutions near the COOH end, M47 (L319R,
       L320S), were able to interact with CREB and the 21-bp repeats to
       assemble ternary Tax-CREB-DNA complexes. As demonstrated earlier, M1,
       M7, and M47 all failed to transactivate the HTLV-I long terminal repeat.
       Our data indicate that the defects in M1 and M7 result from an inability
       to interact with CREB. In contrast, the COOH-terminal mutations in M47
       most likely inactivated the transactivation domain of Tax. As
       anticipated, a Tax mutant, M22 (G137A, L138S) which activated
       transcription from the 21-bp repeats with reduced capacity and was
       defective in trans activating the NF-kappa B binding sites, continued to
       interact with CREB in vitro, albeit with a lower level of efficiency.
       Finally, a glutathione S-transferase (GST)-Tax fusion protein with the
       GST moiety fused to the NH2 terminus of Tax failed to interact with
       CREB. Removal of the GST domain from GST-Tax by thrombin restores Tax's
       ability to assemble a ternary Tax-CREB-21-bp-repeat complex.(ABSTRACT
       TRUNCATED AT 400 WORDS)
 DE    Amino Acid Sequence  Base Sequence  Chimeric Proteins  Consensus
       Sequence  DNA/METABOLISM  DNA Primers/CHEMISTRY  DNA-Binding Protein,
       Cyclic AMP-Responsive/*METABOLISM  Gene Expression Regulation, Viral
       Gene Products, tax/CHEMISTRY/*METABOLISM  Glutathione
       Transferases/GENETICS  HTLV-I/*GENETICS  Molecular Sequence Data
       Mutagenesis, Site-Directed  Protein Binding  Regulatory Sequences,
       Nucleic Acid  Structure-Activity Relationship  Support, Non-U.S. Gov't
       Support, U.S. Gov't, P.H.S.  *Trans-Activation (Genetics)  JOURNAL
       ARTICLE

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).