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Nuclease digestion in between and within nucleosomes
Nucleic Acids Research
|October 1, 1976
Summary
Micrococcal nuclease digestion shortens nucleosomal DNA in rat liver nuclei. Lower temperatures enhance DNA fragmentation, indicating digestion conditions affect accessibility of cleavage sites within nucleosomes.
Area of Science:
- Molecular Biology
- Chromatin Structure
- Biochemistry
Background:
- Nucleosomes are the basic units of DNA packaging in eukaryotes.
- Understanding DNA accessibility within nucleosomes is crucial for gene regulation.
- Micrococcal nuclease is a common enzyme used to probe DNA accessibility in chromatin.
Purpose of the Study:
- To investigate the effect of digestion conditions on nucleosomal DNA fragmentation.
- To analyze the impact of temperature on micrococcal nuclease and DNAase II activity.
- To understand the accessibility of DNA cleavage sites within rat liver nuclei.
Main Methods:
- Digestion of rat liver nuclei with micrococcal nuclease at varying temperatures (0-10°C vs. 40°C).
- Digestion with DNAase II at low temperatures.
- Analysis of DNA fragment sizes using gel electrophoresis (implied).
Main Results:
- Micrococcal nuclease digestion shortened nucleosomal DNA by 50-60 base pairs.
- Lower temperatures (0-10°C) resulted in more DNA fragments between nucleosome sizes compared to 40°C.
- DNAase II favored a 200 base pair pattern at low temperatures.
- Acid-soluble DNA formation was slower than subnucleosomal material formation.
Conclusions:
- Digestion conditions, particularly temperature, significantly influence DNA cleavage site accessibility in nucleosomes.
- Enzyme activity and DNA accessibility are sensitive to environmental factors during chromatin digestion.
- Further investigation into the reasons for temperature-dependent accessibility is warranted.