A coupled DNA-annealing model to explain the unusual ITC titration curves for HMGA2 binding to AT-rich DNA oligomers. a to f represent the partially annealed DNA oligomer, the fully annealed DNA oligomer, the partially unfolded protein, the fully folded protein, the protein-DNA complex with the fully annealed oligomer, the protein-DNA complex with the partially annealed oligomer, respectively. ΔHa, ΔHb, ΔHc, ΔHa', and ΔHb' represents the enthalpy change associated with each step.