Quantitative studies of the effect of HTLV-I Tax protein on CREB protein--DNA binding.
The human T-cell leukemia virus type I (HTLV-I) Tax protein increases the DNA binding activity of a number of different host cell transcription factors, including the cyclic AMP response element binding protein (CREB). We have performed quantitative studies of CREB binding in the presence and absence of Tax in an attempt to gain insight into the mechanism of the Tax effect. Enhancement of binding occurred over a wide range of CREB concentrations, but sharply increased at the lowest concentrations tested. The data are best explained by a two-step binding model where Tax changes the apparent equilibrium constants for both a CREB-CREB dimerization step and a (CREB)2-DNA binding step. We used the model to perform a quantitative analysis of the binding of CREB to DNA that had been mutated at positions flanking the core CREB recognition site. Results suggest that there are altered or more extensive DNA-protein contacts at these positions in the presence of Tax. We also used the model to analyze differences in the interaction of Tax with nonphosphorylated and protein kinase A-phosphorylated CREB protein. There was no significant change in the behavior of CREB upon phosphorylation.
Anderson
M G
MG
Department of Chemistry and Biochemistry, University of Colorado, Boulder 80309.
Dynan
W S
WS
D001483:Base Sequence; D001665:Binding Sites; D017362:Cyclic AMP Response Element-Binding Protein / Q000737:chemistry / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli; D016356:Gene Products, tax / Q000494:pharmacology*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000494:pharmacology; D013329:Structure-Activity Relationship
D017362:Cyclic AMP Response Element-Binding Protein; D016356:Gene Products, tax; D046911:Macromolecular Substances; D011994:Recombinant Proteins; D004247:DNA; D017868:Cyclic AMP-Dependent Protein Kinases