DNA double-strand breaks (DSBs) are cytotoxic DNA lesions that must be repaired as soon as possible because it can cause chromosomal aberrations and cell death. Homologous recombination (HR) and nonhomologous end joining (NHEJ) are the pathways that mainly repair these ruptures. HR process is finely regulated by synchronized posttranslational modifications including phosphorylation, ubiquitylation, and SUMOylation. The ubiquitin (Ub) modifications at damaged chromatin serve as recruitment platforms for DSB repair complexes by facilitating binding sites or regulating the interaction between proteins. Thus, SUMOylation has been associated with protein interaction, enzymatic activity, and chromatin mobility. Several DNA damage factors have been found to be ubiquitylated and SUMOylated including histones (H2AX) and proteins such as Mre11, Rad51, NBS1, and BRCA1. Regarding ubiquitylation-mediated regulation of DNA repair, RNF168 and RNF8 E3 ligases have turned out to be a key step in DNA damage repair regulation. Interestingly, there is evidence that the Ub signaling mechanism is ancestral, and this emphasizes its importance.
Part of the book: Ubiquitination Governing DNA Repair