Dynamics of protein binding to sites of nascent unscheduled DNA repair synthesis in non-proliferating cells

The analysis of DNA repair mechanisms is of fundamental importance to understand how cells remove DNA damage and maintain their genome stability. Investigating the dynamic association of proteins at sites of active DNA synthesis has been successfully performed at DNA replication forks, providing important information on the process, and allowing the identification of new players acting at these sites. However, the applicability of these studies to DNA repair events at sites of nascent unscheduled DNA synthesis (UDS) in non-proliferating cells has been never tested. Here, we describe the analysis of dynamics association of protein participating in nucleotide excision repair (NER), and in other DNA repair processes, at sites of nascent UDS in non-proliferating cells, to avoid interference by DNA replication. Labeling with 5-ethynyl-2'-deoxyuridine (EdU) after DNA damage, followed by click reaction to biotinylate these sites, permits the analysis of dynamic association of proteins, such as DNA polymerases ? and ?, as well as PCNA, to active DNA repair synthesis sites. The suitability of this technique to identify new factors present at active UDS sites is illustrated by two examples of proteins previously unknown to participate in the UV-induced DNA repair process.