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Nucleosome Core Particles Lacking H2B or H3 Tails Are Altered Structurally and Have Differential Base Excision Repair
Paul J Caffrey1, Sarah Delaney1
1Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States.
Biochemistry
|January 11, 2021
Summary
Histone tail clipping alters nucleosome structure, affecting DNA repair. Loss of H2B tails enhances repair of ethenoadenine lesions, while H3 tail loss inhibits it, impacting mutation hotspots.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Post-translational modification of histones, including tail clipping, regulates DNA damage response.
- Nucleosome core particles (NCPs) package DNA, influencing accessibility for repair enzymes.
Purpose of the Study:
- To investigate structural changes in NCPs lacking histone H2B or H3 tails.
- To determine the impact of these structural changes on the excision of ethenoadenine (εA) by alkyladenine DNA glycosylase.
Main Methods:
- Chemical footprinting to analyze NCP structure.
- Global analysis of 21 ethenoadenine sites in NCPs and duplex DNA.
- Assessing repair enzyme activity in the presence and absence of histone tails.
Main Results:
- Absence of H2B or H3 tails alters DNA periodicity within NCPs.
- εA excision is enhanced in tailless H2B NCPs in DNA unwrapping regions.
- εA excision is inhibited in tailless H3 NCPs in static NCP regions.
Conclusions:
- Histone tail removal can facilitate or hinder base excision repair, depending on location and histone type.
- Tail clipping may overcome some DNA packaging obstructions but can inhibit repair in other contexts.
- These findings contribute to understanding mutational hotspots and DNA repair mechanisms.
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