Association of DNA with Nuclear Matrix

Abstract

There is increasing evidence that chromosomal DNA is attached to a nuclear skeleton or matrix. The composition and morphology of the matrix appears to be highly complex in keeping with the long list of known and postulated functions, which seems to include nearly all important processes of the nucleus, such as transcription, RNA processing and transport, replication, and the organization of interphase chromatin. A significant problem is, however, that nuclear matrices are operationally defined structures and that results obtained by use of different methods are not comparable. Depending on various reports, the matrix contains a more-or-less wide spectrum of nonhistone proteins but few of these (mostly enzymes) have been identified (Razin et al. 1981; Smith and Berezney 1983; Staufenbiel and Deppert 1983; Berrios et al. 1985; Jackson and Cook 1986; Lehner et al. 1986; Pieck et al. 1987; Tubo et al. 1987; Tubo and Berezney 1987a, b, c; Fey and Penman 1988). A class of major structural proteins such as the histones in chromatin or the lamins in the nuclear lamina has not yet been found in nuclear matrix preparations. The matrix, when prepared with 2 M NaC1 and DNase I digestion (Berezney and Coffey 1974), further contains less than 1% of the nuclear DNA. Several laboratories have studied the distribution of nuclear DNA in matrices. Repeatedly, actively transcribed genes and their flanking sequences were found to be enriched in nuclear matrices (Jackson et al. 1981; Robinson et al. 1982; Ciejek et al. 1983; Hentzen et al. 1984; Jost and Seldran 1984; Rose and Garrard 1984; Strätling et al. 1986; Strätling 1987). An enrichment of repeated DNA sequences in nuclear matrix preparations was also reported (Goldberg et al. 1983; Chimera and Musich 1985).