[Structural organization of the nucleosomal chromatin fibril under various ionic conditions].
The process of chromatin compactization in nuclei at different concentrations of Mg2+ and/or Na+ ions has been investigated by analysis of chromatin cleavage pattern with DNase II. Nuclei of cells that differ in transcriptional activity and have different nucleosome DNA repeat length such as pigeon erythrocytes, rat cerebellum neurons and pigeon brain cortex neurons were studied. In the presence of 0-3 mM MgCl2 several compactization levels of nucleosomal fiber were revealed in chromatin of pigeon erythrocyte and rat cerebellum nuclei (nucleosome DNA repeat of 210 +/- 3 and 202 +/- 3 nucleotide pairs, respectively). Each of these levels are characterized by different types of periodical DNA fragmentation of chromatin with DNase II, namely formation of nucleosomal, "half-nucleosomal" (fragmentation via a 100 nucleotide pairs interval), and dinucleosomal periodicities. Similar compactization stages were shown also for isolated erythrocyte chromatin. In 0-3 mM MgCl2 chromatin of pigeon brain cortex neuron nuclei having nucleosome DNA repeat size 164 +/- 3 nucleotide pairs is cleaved with DNase II producing only a "half-nucleosomal" periodicity. A pattern of chromatin fragmentation was compared in the presence of Na+ and Mg2+ ions. In the presence of 10-100 mM NaCl or in 0.1-3 mM MgCl2 but in the presence of 50 mM NaCl erythrocyte chromatin condenses in nuclei forming a structure which is characterized only by a "half-nucleosomal" periodicity of fragmentation at DNase II action. Upon higher NaCl concentration (100-400 mM) in the presence of 3 mM MgCl2 a transition from dinucleosomal fragmentation to nucleosomal fragmentation of erythrocyte chromatin in nuclei with DNase I was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002531:Cerebellum / Q000032:analysis; D002843:Chromatin / Q000032:analysis*; D010856:Columbidae; D004587:Electrophoresis, Agar Gel; D004706:Endodeoxyribonucleases; D004912:Erythrocytes / Q000032:analysis; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000032:analysis*; D011487:Protein Conformation; D051381:Rats
D002843:Chromatin; D009707:Nucleosomes; D004706:Endodeoxyribonucleases; C019329:deoxyribonuclease II
Strukturnaia organizatsiia nukleosomnoĭ fibrilly khromatina v razlichnykh ionnykh usloviiakh.