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Histone shuttling by poly ADP-ribosylation
F R Althaus1, L Höfferer, H E Kleczkowska
1University of Zürich-Tierspital, Institute of Pharmacology and Toxicology, Switzerland.
Molecular and Cellular Biochemistry
|September 1, 1994
Summary
The enzymes poly(ADP-ribose)polymerase and poly(ADP-ribose) glycohydrolase work together in a histone shuttle mechanism. This process helps DNA repair by making damaged DNA accessible and then reassembling chromatin.
Area of Science:
- Molecular Biology
- Epigenetics
- DNA Repair Mechanisms
Background:
- Chromatin structure, regulated by histones, plays a crucial role in DNA accessibility.
- DNA strand breaks trigger cellular responses, including DNA repair pathways.
- The enzymes poly(ADP-ribose)polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG) are involved in chromatin regulation.
Purpose of the Study:
- To elucidate the cooperative mechanism between PARP and PARG in chromatin dynamics.
- To investigate the role of a histone shuttle mechanism in DNA repair.
- To understand how PARP and PARG facilitate nucleosomal unfolding and DNA accessibility.
Main Methods:
- Investigated the enzymatic activities of PARP and PARG in response to DNA strand breaks.
- Examined the interaction of PARP's N-terminal domain with DNA and its catalytic activation.
- Studied the role of ADP-ribose polymers in histone displacement and reassociation.
Main Results:
- PARP activation by DNA strand breaks leads to histone displacement via ADP-ribose polymer formation.
- PARG sequentially degrades ADP-ribose polymers, facilitating histone reassociation with DNA.
- This enzyme cooperation creates an accessible chromatin environment around DNA breaks.
Conclusions:
- PARP and PARG cooperate to drive a histone shuttle mechanism essential for DNA repair.
- Histone shuttling, involving displacement and reassociation, acts as a catalyst for nucleosomal unfolding.
- This mechanism enhances the accessibility of DNA strand break sites for repair proteins.