Our most recent work [Hibino et al. (1995)
Cancer Lett., 88, 49-55] has shown that the selective binding affinities of highly repetitive
DNA components for a
nuclear scaffold protein from rat
ascites hepatoma cells (
P230) depend on the degree of sequence-directed bending of the helix axis. In the present experiment, this
protein has been highly purified and isolated by a series of column chromatographic procedures to migrate as a single band to a molecular weight position of 230 kd on a SDS-
polyacrylamide gel. A filter binding assay showed that the binding of a repetitive AT-rich component (369 bp XmnI fragment) from the
hepatoma nucleus, which has a strongly bent overall structure, to isolated
P230 is based on a cooperative mode of interaction.
Distamycin A, which binds specifically to AT-rich
DNA, removed the bend in the XmnI fragment and inhibited binding to this
protein. These results suggest that AT-rich regions in highly repetitive
DNA cause bending of the helix axis to be recognized by
nuclear scaffold protein(s). Moreover, it has been shown that the nuclear scaffold fraction from rat liver or an actively growing hepatocyte cell line (Ac2F cells) does not contain
P230, but does have a repetitive bent
DNA binding protein (P130), which has an apparent molecular weight of 130 kd. In addition, the immunoblot analysis showed that mouse anti-P130 antiserum reacts with
P230. Thus, the results in the present study imply that there is some difference in the higher order structure of the nuclear
DNA attachment region between rat liver or actively growing hepatocytes and the
hepatoma, although
P230 appears to be immunochemically similar to P130.