The basic/helix-loop-helix/leucine zipper (b/HLH/Z) transcription factor upstream stimulatory factor (USF) and its isolated DNA binding domain undergo a random coil to alpha-helix folding transition on recognizing their cognate DNA. The USF b/HLH cocrystal structure resembles the structure of the b/HLH/Z domain of the homologous protein Max and reveals (i) that the truncated, b/HLH DNA binding domain homodimerizes, forming a parallel, left-handed four-helix bundle, and (ii) that the basic region becomes alpha-helical on binding to the major groove of the DNA sequence CACGTG. Hydrodynamic measurements show that the b/HLH/Z DNA binding domain of USF exists as a bivalent homotetramer. This tetramer forms at the USF physiological intranuclear concentration, and depends on the integrity of the leucine zipper motif. The ability to bind simultaneously to two independent sites suggests a role in DNA looping for the b/HLH/Z and Myc-related families of eukaryotic transcription factors.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Reference||Annotation Extension|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Conditions||Strain||Source||Reference|