The association of the interspersed repetitive KpnI sequences with the nuclear matrix.

The KpnI sequences constitute the dominant, long, interspersed repetitive DNA families in primate genomes. These families contain related, but nonidentical sequence subsets, some of which border functional gene domains and are transcribed into RNA. To test whether these sequences perform an organizational function in the nucleus, their association with the nuclear matrix has been examined in African green monkey cells. DNase I treatment depleted the residual matrix of most of the KpnI 1.2- and 1.5-kilobase pair family sequences although significant amounts of each family remained in the loop attachment DNA fragments. Hybridization analysis of the KpnI and RsaI cleavage patterns of matrix loop attachment DNA indicate that some sequence subsets of these KpnI families are relatively less depleted than others. The nuclear matrix association of subpopulations of KpnI 1.2- and 1.5-kilobase pair families was also shown by metrizamide gradient centrifugation of nuclear matrix complexes cleaved by KpnI endonuclease. The gradients demonstrate that some KpnI segments are differentially associated with nuclear matrix proteins. Moreover, the procedures permit the preparative isolation and purification of the DNA-protein complexes containing these KpnI 1.2- and 1.5-kilobase pair sequence families. Speculations on the relationship between the matrix association of these KpnI family sequences and their possible roles in gene organization and expression are presented and discussed.