Related Experiment Videos
Isolation of high mobility group-containing mononucleosomes from avian erythrocyte nuclei and their sensitivity to
Abstract:
Conditions have been established which have led to the isolation of mononucleosomes which contain the high mobility group (HMG) proteins, in particular HMG 14, from mature chicken erythrocyte nuclei after extended micrococcal nuclease digestion. This selective enhancement of HMG-containing mononucleosomes appears to be due to their preferential solubilization at a time when other mononucleosomes, i.e. those containing H5 and H1 which represent the bulk of the mononucleosomes, were no longer soluble. Isolation of "early" mononucleosomes and subsequent analysis of these mononucleosomes after DNase I digestion showed that the DNA of these "early" mononucleosomes was more accessible to DNase I and that those mononucleosomes which contained HMG 14 were more soluble when the DNA became extensively degraded by DNase I. The resulting pattern of single-stranded DNA fragments suggests that the NH2 termini of the core histones no longer bind strongly to the nucleosomal DNA of the "early" mononucleosomes, and thus enhance the rate of DNase I digestion, while the presence of HMG 14 increased the solubility of these mononucleosomes. These two properties are probably the basis for the increased DNase I sensitivity of the transcriptionally active chromatin.
Insights
High mobility group (HMG) proteins, like HMG 14, are selectively isolated in soluble mononucleosomes from chicken red blood cells. These HMG-containing nucleosomes exhibit increased DNA accessibility and solubility, indicating a role in active chromatin structure.
Area of Science:
- Molecular Biology
- Chromatin Structure and Dynamics
- Epigenetics
Background:
- Mature chicken erythrocyte nuclei contain distinct mononucleosomes associated with different proteins.
- High mobility group (HMG) proteins, including HMG 14, are known to interact with chromatin.
- Understanding nucleosome solubility and DNA accessibility is crucial for deciphering chromatin function.
Purpose of the Study:
- To establish conditions for isolating mononucleosomes enriched in HMG proteins from chicken erythrocyte nuclei.
- To investigate the relationship between HMG 14, DNA accessibility, and nucleosome solubility.
- To explore the role of these properties in transcriptionally active chromatin.
Main Methods:
- Extended micrococcal nuclease digestion of mature chicken erythrocyte nuclei.
- Selective solubilization and isolation of mononucleosomes.
- DNase I digestion analysis of isolated mononucleosomes to assess DNA accessibility and solubility.
Main Results:
- Mononucleosomes containing HMG 14 were selectively solubilized and isolated.
- These HMG-containing mononucleosomes showed increased DNA accessibility to DNase I.
- HMG 14 presence correlated with enhanced mononucleosome solubility, particularly with extensive DNA degradation.
Conclusions:
- HMG 14 contributes to the preferential solubilization of mononucleosomes.
- The NH2 termini of core histones in early mononucleosomes exhibit reduced DNA binding, increasing DNase I sensitivity.
- Increased DNase I sensitivity and solubility of HMG-containing mononucleosomes are likely key features of transcriptionally active chromatin.