Properties of an adenosine triphosphate-stimulated factor that enhances the nuclear binding of activated glucocorticoid-receptor complex: binding to histone-agarose.

Recently we have purified and characterized a factor in rat liver cytosol that enhances nuclear binding of the activated glucocorticoid-receptor complex in the presence of ATP [an ATP-stimulated translocation promoter (ASTP)]. It has a mol wt of 93,000, S value of 6.5, and pI of 4.5. Here we report studies on the binding of ASTP to histones from calf thymus. Higher salt concentrations were required to disrupt the binding of ASTP to histone-agarose than to disrupt its binding to the anion exchanger diethylaminoethyl-cellulose (half-maximal concentration for inhibition: 200 mM vs. 60 mM KCl). ATP decreased the binding of ASTP to histone-agarose in a dose-dependent fashion, but ADP and AMP had no appreciable effect on the binding. Pyridoxal 5'-phosphate (10 mM) inhibited the binding of ASTP to histone-agarose, whereas 10 mM pyridoxal, pyridoxamine 5'-phosphate, pyridoxamine, and pyridoxine were not inhibitory. ASTP did not bind to histone-agarose that had been pretreated with pyridoxal 5'-phosphate and then reduced with sodium borohydride. In contrast, ASTP pretreated in the same way could bind to histone-agarose. Therefore, modification of lysine residues of histones by pyridoxal 5'-phosphate (Schiff base) presumably inhibited the binding of ASTP to the immobilized histone. Competition experiments with various histones (H1, H2A, H2B, H3, and H4) indicated that ASTP bound to the arginine-rich histones H3 and H4, with preference for H4. These observations together suggest that lysine residues in H4 and H3 are essential for the binding of ASTP to histone. The implications of this interaction are discussed.