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Human DNA ligase I efficiently seals nicks in nucleosomes
D R Chafin1, J M Vitolo, L A Henricksen
1Department of Biochemistry and Biophysics, University of Rochester Medical Center, 601 Elmwood Avenue, Rochester, NY 14642, USA.
The EMBO Journal
|October 18, 2000
Summary
Human DNA ligase I efficiently processes DNA on nucleosomes, crucial for Okazaki fragment completion and DNA repair. Its activity is influenced by histone tails, suggesting a broader role in chromatin dynamics.
Area of Science:
- Molecular Biology
- Epigenetics
- DNA Replication and Repair
Background:
- DNA accessibility within nucleosomes is limited for enzymes.
- DNA ligase I is essential for Okazaki fragment processing and DNA repair.
Purpose of the Study:
- To investigate the ability of human DNA ligase I to access and act on nucleosomal DNA.
- To determine the influence of histone modifications on DNA ligase I activity.
Main Methods:
- In vitro assays using purified human DNA ligase I and reconstituted nucleosomes.
- Enzymatic activity assays measuring DNA ligation efficiency.
Main Results:
- Human DNA ligase I efficiently accesses and ligates DNA wrapped around nucleosomes in vitro.
- Ligase activity is unaffected by linker histone H1 binding.
- Core histone tail domain disposition significantly influences ligase activity.
Conclusions:
- Human DNA ligase I can function on nucleosomal DNA, extending its role beyond initial chromatin reassembly.
- Histone tail interactions are critical regulators of DNA ligase I activity at chromatin sites.