Abstract 16004: Crystal Structure of TBX5 DNA Binding Domain and NKX2.5 Homeodomain in Complex With ANF-252 Motif
Background Heart morphogenesis is controlled by combinatorial interactions of core cardiac transcription factors such as TBX5 and NKX2.5. Mutations in TBX5 and NKX2.5 result in congenital heart diseases including Holt-Oram syndrome, atrial and ventricular septal defects, and tetralogy of Fallot. TBX5 and NKX2.5 co-occupy promoters/enhancers of downstream targets and interact with each other, but details of their interaction are not known. One downstream target, atrial natriuretic factor (ANF) contains closely spaced TBX5 and NKX2.5 binding motifs at the -252 site of its proximal promoter. We hypothesize that there are interactions between DNA binding domain (DB) of TBX5 and homeodomain (HD) of NKX2.5 on this sequence. We tested this by solving crystal structure of the TBX5 DB and NKX2.5 HD in complex with ANF-252 DNA.
Methods and Results Crystal structure of human NKX2.5 HD (AA138-197) and TBX5 DB (AA58-238) in complex with 19 base pair ANF-252 DNA was determined at 3.0 Å resolution with current R-work and R-free values of 0.207 and 0.283, respectively. Two complexes of TBX5 DB/NKX2.5 HD/ANF-252 were present in an asymmetric unit (Figure). Extensive interactions between the two TBX5 DBs bound to separate DNAs were observed. Similar interactions were previously observed in TBX5 DB structure, although TBX5 presents as a monomer in solution. Interactions between proteins and DNA are preserved consistent with previous reports. Physical interactions between TBX5 DB and NKX2.5 HD bound on the same ANF-252 DNA were observed at Lys158 (NKX2.5), Asp140 (TBX5) and Pro142 (TBX5), residues that are highly conserved in TBX and NKX families across species.
Conclusions TBX5 DB and the NKX2.5 HD interact with each other to form a heterodimer while bound to the ANF-252 promoter. The structure of the core cardiac transcription factor complex reported here provides detailed pictures of their interactions.
- Congenital heart disease
- Heart development
- Atrial septal defect
- Ventricular septal defect
- Tetralogy of Fallot
- © 2011 by American Heart Association, Inc.