Put a RING on it: regulation and inhibition of RNF8 and RNF168 RING finger E3 ligases at DNA damage sites

Abstract

RING (Really Interesting New Gene) domain-containing E3 ubiquitin ligases comprise a large family of enzymes that in combination with an E2 ubiquitin-conjugating enzyme, modify target proteins by attaching ubiquitin moieties. A number of RING E3s play an essential role in the cellular response to DNA damage highlighting a crucial contribution for ubiquitin-mediated signaling to the genome surveillance pathway. Among the RING E3s, RNF8 and RNF168 play a critical role in the response to double stranded breaks, one of the most deleterious types of DNA damage. These proteins act as positive regulators of the signaling cascade that initiates at DNA lesions. Inactivation of these enzymes is sufficient to severely impair the ability of cells to respond to DNA damage. Given their central role in the pathway, several layers of regulation act at this nodal signaling point. Here we will summarize current knowledge on the roles of RNF8 and RNF168 in maintaining genome integrity with particular emphasis on recent insights into the multiple layers of regulation that act on these enzymes to fine-tune the cellular response to DNA lesions.

Identification of RNF168 as a PML nuclear body regulator

“…To date, RNF8 and RNF168 are known for their important roles in the DDR to double-stranded DNA breaks (Bartocci and Denchi, 2013;Al-Hakim et al, 2010). K63-linked ubiquitylation of histones H2A and/or H2AX and/or other proteins by RNF8 at DSBs results in the recruitment of RNF168, which interacts with the ubiquitylated histones through its three ubiquitinbinding motifs (UMI, MIU1, MIU2) (Stewart et al, 2009;Bartocci and Denchi, 2013;Panier and Durocher, 2009;Panier et al, 2012;Mailand et al, 2007;Doil et al, 2009). Further ubiquitylation of H2A and/or H2AX by RNF168 and RNF8 then leads to recruitment of additional DNA-repair proteins, including 53BP1 and BRCA1.…”

ATDC (Ataxia Telangiectasia Group D Complementing) Promotes Radioresistance through an Interaction with the RNF8 Ubiquitin Ligase

“…RNF8 and its partner RNF168 are RING domain-containing ubiquitin ligases that are recruited to DNA DSB following H2AX phosphorylation by MDC1 (29). Following DNA damage, RNF8 and RNF168 catalyze the addition of ubiquitin to H2A and H2AX and recruitment of 53BP1 and BRCA1 to DNA damage sites, facilitating repair.…”

Ubiquitin-specific Protease 7 Regulates Nucleotide Excision Repair through Deubiquitinating XPC Protein and Preventing XPC Protein from Undergoing Ultraviolet Light-induced and VCP/p97 Protein-regulated Proteolysis

“…Interestingly, the formation of FK2 foci (sites of ubiquitin conjugates detected by anti-ubiquitin FK2 antibody) was severely compromised in these cells. It is known that FK2 foci are formed through lysine 63-linked ubiquitination of H2A/ ␥H2AX by the concerted action of RNF8 and RNF168 E3 ligases (28). However, it is currently unclear why loss of USP7 has a profound impact on the formation of FK2 foci.…”