cAMP response element-binding protein monomers cooperatively assemble to form dimers on DNA.
We have analyzed the properties of cAMP response element-binding protein (CREB) in solution with emphasis on dimerization and effects of phosphorylation. Using a purified CREB fusion protein, a novel dye-label technique, and sedimentation equilibrium analysis, we directly and conclusively demonstrate that, unlike Jun and Fos, CREB dimerization is DNA-dependent. CREB exists primarily as a monomer in solution and cooperatively assembles on DNA to form dimers. Sedimentation equilibrium analysis also indicates that dimerization is unaffected by cAMP-dependent protein kinase-phosphorylation or by the symmetry of the cAMP-responsive element binding site. Filter binding assays reveal that CREB binding is unaffected by phosphorylation regardless of the symmetry of the cAMP-responsive element binding site. Our results suggest that structurally similar members of the same bZIP superfamily may differ significantly in their regulation at the level of dimerization.
Department of Pharmacology, Mayo Foundation and Graduate School, Rochester, Minnesota 55905, USA.
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D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002522:Chlorocebus aethiops; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D019281:Dimerization; D010766:Phosphorylation; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D017362:Cyclic AMP Response Element-Binding Protein; D011993:Recombinant Fusion Proteins; D004247:DNA; D017868:Cyclic AMP-Dependent Protein Kinases