Abstract
Protein poly-ADP-ribosylation (PARylation) is a post-translational modification formed by transferring successive units of ADP-ribose to target proteins to form poly-ADP-ribose (PAR) chains. PAR plays a critical role in the DNA damage response (DDR) by acting as a signaling platform to promote the recruitment of DNA repair factors to the sites of DNA damage that bind via their PAR-binding domains (PBDs). Several classes of PBD families have been identified, which recognize distinct parts of the PAR chain. Proteins encoding PBDs play an essential role in conveying the PAR-mediated signal through their interaction with PAR chains, which mediates many cellular functions, including the DDR. The WWE domain, encoded in 12 human proteins, identifies the iso-ADP-ribose moiety of the PAR chain. PARylation is a heterogeneous structure that is highly dynamic in cells. Capturing the dynamics of PARylation is essential to understanding its role in the DDR, which can be achieved by expanding the tool kit for PAR detection and tracking mediated by the unique binding capability of various sensors. We recently described the WWE domain of RNF146 as a robust genetically encoded probe, when fused to EGFP, for the detection of PAR in live cells. Expanding on this, we used structural prediction tools to evaluate all of the WWE domains encoded in human proteins, evaluating each as molecular PAR probes in live cells. We demonstrate unique PAR dynamics when tracked by WWE-encoded PAR binding domains, in addition to an engineered macrodomain, that can be exploited for modulation of the PAR-dependent DNA damage response.