title: The B-box dominates SAP-1-SRF interactions in the structure of the ternary complex.
abstract: The serum response element (SRE) is found in several immediate-early gene promoters. This DNA sequence is necessary and sufficient for rapid transcriptional induction of the human c-fos proto-oncogene in response to stimuli external to the cell. Full activation of the SRE requires the cooperative binding of a ternary complex factor (TCF) and serum response factor (SRF) to their specific DNA sites. The X-ray structure of the human SAP-1-SRF-SRE DNA ternary complex was determined (Protein Data Bank code 1hbx). It shows SAP-1 TCF bound to SRF through interactions between the SAP-1 B-box and SRF MADS domain in addition to contacts between their respective DNA-binding motifs. The SAP-1 B-box is part of a flexible linker of which 21 amino acids become ordered upon ternary complex formation. Comparison with a similar region from the yeast MATalpha2-MCM1-DNA complex suggests a common binding motif through which MADS-box proteins may interact with additional factors such as Fli-1.
authors.affiliation: ETH Zürich, Institut für Molekularbiologie und Biophysik, ETH-Hönggerberg, CH-8093 Zürich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Hassler
authors.forename: T J
authors.initials: TJ
authors.lastname: Richmond
mesh_terms: D000595:Amino Acid Sequence; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D009690:Nucleic Acid Conformation; D017433:Protein Structure, Secondary; D000090063:Proto-Oncogene Mas; D012045:Regulatory Sequences, Nucleic Acid; D049231:Saposins; D026362:Serum Response Factor; D049128:Sphingolipid Activator Proteins
chemical_list: D004268:DNA-Binding Proteins; D006023:Glycoproteins; C000715470:MAS1 protein, human; D009687:Nuclear Proteins; C483345:PSAP protein, human; D000090063:Proto-Oncogene Mas; D049231:Saposins; D026362:Serum Response Factor; D049128:Sphingolipid Activator Proteins; D004247:DNA