[The murine nuclear matrix protein specificcaly binds to centromeric satellite DNA]

The nuclear matrix (NM) of mouse contains a protein (miSat BP) that can specifically bind to mouse centromeric minor satellite DNA as shown by gel shift assay. The ion-exchange chromatography on DEAE-Sepharose was used as the first miSat BP purification. MiSat BT was eluted by 0.2 M NaCl. Antibodies against p70, a human NM protein of 70 kDa described earlier as a protein recognizing human alphoid DNA, produce hypershift effect when added to the retardation incubation mix. Immunoblotting of NM and an active NM fraction (0.2 M NaCl) with these antibodies revealed a protein with 70 kDa in both preparations. This antigen retained in NM in situ being associated with residual DNA as shown by indirect immunofluorescent staining. In the untreated interphase nucleus most of miSat BP granules were shown to be colocalized with prekinetochores. We suggest that miSat BP is capable of recognizing the minor satellite DNA due to its structural features, but it does not belong to a group of constitutive centromeric proteins.