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Laser Microirradiation to Study In Vivo Cellular Responses to Simple and Complex DNA Damage
Published on: January 31, 2018
Poly(ADP-ribosyl)ation enhances nucleosome dynamics and organizes DNA damage repair components within biomolecular
Michael L Nosella1, Tae Hun Kim2, Shuya Kate Huang2
1Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada.
Abstract:
Nucleosomes, the basic structural units of chromatin, hinder recruitment and activity of various DNA repair proteins, necessitating modifications that enhance DNA accessibility. Poly(ADP-ribosyl)ation (PARylation) of proteins near damage sites is an essential initiation step in several DNA-repair pathways; however, its effects on nucleosome structural dynamics and organization are unclear. Using NMR, cryoelectron microscopy (cryo-EM), and biochemical assays, we show that PARylation enhances motions of the histone H3 tail and DNA, leaving the configuration of the core intact while also stimulating nuclease digestion and ligation of nicked nucleosomal DNA by LIG3. PARylation disrupted interactions between nucleosomes, preventing self-association. Addition of LIG3 and XRCC1 to PARylated nucleosomes generated condensates that selectively partition DNA repair-associated proteins in a PAR- and phosphorylation-dependent manner in vitro. Our results establish that PARylation influences nucleosomes across different length scales, extending from the atom-level motions of histone tails to the mesoscale formation of condensates with selective compositions.
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