The B-Box Dominates Sap-1/Srf Interactions in the Structure of the Ternary Complex
Hassler, M., Richmond, T.J.(2001) EMBO J 20: 3018
- PubMed: 11406578 
- DOI: https://doi.org/10.1093/emboj/20.12.3018
- Primary Citation of Related Structures:  
1HBX - PubMed 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.
Organizational Affiliation: 
ETH Zürich, Institut für Molekularbiologie und Biophysik, ETH-Hönggerberg, CH-8093 Zürich, Switzerland.