Ewing sarcoma protein promotes dissociation of poly( ADP ‐ribose) polymerase 1 from chromatin

Abstract

Poly(ADP‐ribose) polymerase 1 (PARP1) facilitates DNA damage response (DDR). While the Ewing's sarcoma breakpoint region 1 (EWS) protein fused to FLI1 triggers sarcoma formation, the physiological function of EWS is largely unknown. Here, we investigate the physiological role of EWS in regulating PARP1. We show that EWS is required for PARP1 dissociation from damaged DNA. Abnormal PARP1 accumulation caused by EWS inactivation leads to excessive Poly(ADP‐Ribosy)lation (PARylation) and triggers cell death in both in vitro and in vivo models. Consistent with previous work, the arginine‐glycine‐glycine (RGG) domain of EWS is essential for PAR chain interaction and PARP1 dissociation from damaged DNA. Ews and Parp1 double mutant mice do not show improved survival, but supplementation with nicotinamide mononucleotides extends Ews‐mutant pups’ survival, which might be due to compensatory activation of other PARP proteins. Consistently, PARP1 accumulates on chromatin in Ewing's sarcoma cells expressing an EWS fusion protein that cannot interact with PARP1, and tissues derived from Ewing's sarcoma patients show increased PARylation. Taken together, our data reveal that EWS is important for removing PARP1 from damaged chromatin.

Biomolecular condensates at sites of DNA damage: More than just a phase

“…Due to two phosphate groups per ADP-ribose unit, PAR is a highly negatively charged polymer, which during the peak of PAR production recruits a plethora of PAR-binding proteins by multivalent electrostatic interactions, including FUS, EWS and TAF15 [ 171 ]. While the prion-like N-termini of the FET proteins undergo concentration-dependent phase separation and form liquid droplets in cells, their positively charged RG/RGG-rich C-termini confer affinity to anionic PAR [ 68 , 172 , 173 ]. Interestingly, polyelectrolyte interactions can lead to ultrahigh affinity complexes in which the binding partners retain their structural disorder and highly dynamic character [ 174 , 175 ], implying that high affinity binding and structural disorder within complexes are not mutually exclusive.…”

“…The FUS-related proteins EWS and TAF15 show very similar transient recruitment behavior and co-assemble into PAR-seeded compartments [ 68 , 172 , 173 ], and several additional RNA- and PAR-binding proteins, including hnRNPs and hnRNP-like proteins, also get transiently enriched in PAR-seeded condensates [ 171 , 184 ]. While according to the scaffold and client model some of these RNA- and PAR-binding proteins likely play more important roles than others for the local demixing that occurs around DNA break sites, it seems reasonable to assume that collectively they shape the local environment and its viscoelastic properties.…”

A genetically encoded photo-proximity labeling approach for mapping protein territories

“…39 For example, the top hits on the list, FUS and EWSR1, are RNA-binding proteins that participate in DNA repair and localize to DNA breaks through PAR binding. 40,41 We were particularly intrigued by the high enrichment of HMGB1, a multifunctional chromatin-associated protein implicated in various DNA repair pathways. 42 HMGB1 accumulates at sites of DNA damage; 43 however, the mechanism for this process is not yet understood.…”

A Double-Edged Sword: The Two Faces of PARylation

“…Rapid PAR degradation is essential for cellular homeostasis and genomic stability. Hyper-PARylation or accumulation of PAR in chromatin induces genomic instability and/or cell death [ 48 ]. PARylated PARP-1 dissociates PARP-1 from the DNA damage site [ 49 ].…”