title: DNA binding site selection of dimeric and tetrameric Stat5 proteins reveals a large repertoire of divergent tetrameric Stat5a binding sites.
abstract: We have defined the optimal binding sites for Stat5a and Stat5b homodimers and found that they share similar core TTC(T/C)N(G/A)GAA interferon gamma-activated sequence (GAS) motifs. Stat5a tetramers can bind to tandemly linked GAS motifs, but the binding site selection revealed that tetrameric binding also can be seen with a wide range of nonconsensus motifs, which in many cases did not allow Stat5a binding as a dimer. This indicates a greater degree of flexibility in the DNA sequences that allow binding of Stat5a tetramers than dimers. Indeed, in an oligonucleotide that could bind both dimers and tetramers, it was possible to design mutants that affected dimer binding without affecting tetramer binding. A spacing of 6 bp between the GAS sites was most frequently selected, demonstrating that this distance is favorable for Stat5a tetramer binding. These data provide insights into tetramer formation by Stat5a and indicate that the repertoire of potential binding sites for this transcription factor is broader than expected.
authors.affiliation: Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, Maryland 20892, USA.
authors.forename: E
authors.initials: E
authors.lastname: Soldaini
authors.forename: S
authors.initials: S
authors.lastname: John
authors.forename: S
authors.initials: S
authors.lastname: Moro
authors.forename: J
authors.initials: J
authors.lastname: Bollenbacher
authors.forename: U
authors.initials: U
authors.lastname: Schindler
authors.forename: W J
authors.initials: WJ
authors.lastname: Leonard
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008894:Milk Proteins; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D050799:STAT5 Transcription Factor; D016415:Sequence Alignment; D015398:Signal Transduction; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins
chemical_list: D004268:DNA-Binding Proteins; D008894:Milk Proteins; D050799:STAT5 Transcription Factor; C494092:STAT5A protein, human; C494095:STAT5B protein, human; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D004247:DNA