KIX-mediated assembly of the CBP-CREB-HTLV-1 tax coactivator-activator complex.
The HTLV-1 transcriptional activator Tax is required for viral replication and pathogenesis. In concert with human CREB, Tax recruits the human transcriptional coactivator and histone acetyltransferase p300/CBP to the HTLV-1 promoter. Here we investigate the structural features of the interaction between Tax and the KIX domain of p300/CBP. Circular dichroism spectroscopy, nuclear magnetic resonance chemical shift perturbation mapping, and sedimentation equilibrium analysis show that KIX binds a Tax subdomain corresponding to residues 59-98 of Tax (called Tax(59-98)). Circular dichroism spectroscopy suggests that Tax(59-98) is intrinsically disordered (natively unfolded) in isolation and adopts an ordered conformation upon binding KIX. The interaction is disrupted by a single amino acid variation of Tax(59-98) in which leucine 68 is substituted with proline. Chemical shift perturbation mapping reveals that the Tax-binding surface of KIX is distinct from that utilized by CREB, and corresponds to the site of KIX that interacts with the human transcription factors c-Jun and mixed lineage leukemia protein (MLL). Sedimentation equilibrium analysis shows that Tax and the phosphorylated KID domain of CREB can simultaneously bind KIX to form a ternary 1:1:1 complex. The results provide a molecular description of the concerted recruitment of p300/CBP via the KIX domain by Tax and phosphorylated CREB during Tax-mediated gene expression.
Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523-1870, USA.
Andrew C
AC
Vendel
Steven J
SJ
McBryant
Kevin J
KJ
Lumb
D002942:Circular Dichroism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D016356:Gene Products, tax / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D009687:Nuclear Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*
D017362:Cyclic AMP Response Element-Binding Protein; D016356:Gene Products, tax; D009687:Nuclear Proteins; D015534:Trans-Activators