Biophysical characterization of interactions between the core binding factor alpha and beta subunits and DNA

Core binding factors (CBFs) play key roles in several developmental pathway s and in human disease. CBFs consist of a DNA binding CBF alpha subunit and a non-DNA binding CBF beta subunit that increases the affinity of CBF alph a for DNA. We performed sedimentation equilibrium analyses to unequivocally establish the stoichiometry of the CBF alpha:beta:DNA complex. Dissociatio n constants for all four equilibria involving the CBF alpha Runt domain, CB F beta, and DNA were defined. Conformational changes associated with intera ctions between CBF alpha, CBF beta, and DNA were monitored by nuclear magne tic resonance and circular dichroism spectroscopy. The data suggest that CB F beta 'locks in' a high affinity DNA binding conformation of the CBF alpha Runt domain. (C) 2000 Federation of European Biochemical Societies.