A structure of potentially active and inactive genes of chicken erythrocyte chromatin upon decondensation

Abstract

In the presence of 3 mM MgCl2 DNase I cleavage of bulk, globin and ovalbumin gene chromatin in chicken erythrocyte nuclei generates fragments which are multiples of a double-nucleosome repeat. However, in addition to the dinucleosomal periodicity beta-globin gene chromatin was fragmented into multiples of a 100 b.p. interval which is characteristic for partially unfolded chromatin. This distinction correlates with higher sensitivity of beta-globin domain to DNase I and DNase II as compared to the inactive ovalbumin gene. At 0.7 mM MgCl2 where these DNases fragment bulk chromatin into series of fragments with a 100 b.p. interval, the difference in digestibility of the investigated genes is dramatically decreased. When chromatin has been decondensed by incubation of nuclei in 10 mM Tris-buffer, DNase II generates a typical nucleosomal repeat, and the differential nuclease sensitivity of the analyzed genes is not observed. The data suggest that higher nuclease sensitivity of potentially active genes is due to irregularities in higher order chromatin structure.

Transcription-induced nucleosome ‘splitting’: an underlying structure for DNase I sensitive chromatin.

“…Although we have not detected split nucleosomes within the 3 '-region of the expressed CIN2 gene, this gene is transcribed at a much lower frequency than the basally-transcribed HSP82 gene (unpublished results) and therefore, the CIN2 gene probably lacks traversing RNA polymerase molecules in the major fraction of cells. Furthermore previous studies have detected a weak half-nucleosomal repeat in DNase I digests of bulk chromatin isolated from yeast cells, chicken erythrocytes and HeLa cells (Lohr and Van Holde , 1979;Kukushkin et at., 1988). Thus, taken together with our results, it seems likely that split nucleosomes are of common occurrence and may represent one of the underlying structures of DNase I sensitive chromatin (Weintraub and Groudine, 1976).…”

“…1987), and the chicken fl-globin gene (Kukushkin et at., 1988). Furthermore previous studies have detected a weak half-nucleosomal repeat in DNase I digests of bulk chromatin isolated from yeast cells, chicken erythrocytes and HeLa cells (Lohr and Van Holde , 1979;Kukushkin et at., 1988). Furthermore previous studies have detected a weak half-nucleosomal repeat in DNase I digests of bulk chromatin isolated from yeast cells, chicken erythrocytes and HeLa cells (Lohr and Van Holde , 1979;Kukushkin et at., 1988).…”

“…However, in the cases where DNase I has been used, apparent split nucleosomes have been seen along transcribing Drosophita hsp22 and 26 genes (Cartwright and Elgin, 1986), the yeast SUC2 gene (Perez-Ortin et at.,. 1987), and the chicken fl-globin gene (Kukushkin et at., 1988). Although we have not detected split nucleosomes within the 3 '-region of the expressed CIN2 gene, this gene is transcribed at a much lower frequency than the basally-transcribed HSP82 gene (unpublished results) and therefore, the CIN2 gene probably lacks traversing RNA polymerase molecules in the major fraction of cells.…”

Chromatin Polymorphism and the Nucleosome Superfamily: A Genealogy

“…DNase I or II digestions of erythrocyte nuclei were found to result in DNA fragments of sizes consistent with a relatively resistant structure of two nucleosomes [33][34][35] called nucleodisome (quote from ref. 34: "the pigeon erythrocyte contains a particular structural unit consisting of two nucleosomes.…”

Loosened nucleosome linker folding in transcriptionally active chromatin of chicken embryo erythrocyte nuclei

“…The structural basis of general chromatin activation marked by the DNase-I sensitivity remains obscure. It has been variously attributed to a loss of linker histones (6,7), to an association with nonhistone proteins HMG 14/17 (8), to an altered supranucleosome chromatin folding (9,10), to a rearrangement of nucleosome core structure (1 1, 12), and even to a preffered location at the nuclear periphery (13,14).…”