INVOLVEMENT OF PHOSPHORYLATION IN BINDING OF NUCLEAR SCAFFOLD PROTEINS FROM RAT-LIVER TO A HIGHLY REPETITIVE DNA COMPONENT

The results of our previous work [Hibino et al., Biochim. Biophys. Act a 1174 (1993) 162-170] suggested that a highly repetitive DNA componen t facilitates bending of the helix axis to be recognized by the nuclea r scaffold proteins from rat liver, P123 and P130. In the present expe riment, it was shown that binding of these proteins to such a repetiti ve DNA component from rat liver nuclei (370-bp XmnI fragment) is based on a cooperative mode of interaction, although the binding activity o f P130 is much higher than that of P123. The immunoblot analysis with anti-phosphoamino acid antibodies suggested that phosphorylation of se rine and threonine residues occurs on P123 and P130, but also of tyros ine residue(s) on P130. The phosphatase assay showed that phosphoryl g roups on these proteins may be involved in altering the DNA binding ac tivities of the proteins. Thus, the results in the present study imply that phosphorylation of a nuclear scaffold protein in addition to the degree of bending of the DNA helix axis plays an important role in an choring chromatin to the nuclear scaffold and in construction of a hig her-order chromatin structure. (C) 1998 Elsevier Science B.V.