Initially, it was believed that SCR7 could block non-homologous end joining (NHEJ) mediated DNA repair by inhibiting DNA ligase IV, resulting in the increase of the genome editing efficiency of CRISPR-Cas9.
1-4) However, researchers found later that the major product which was formed from the initial synthetic method was
SCR7 pyrazine, not SCR7, and SCR7 itself could not inhibit DNA ligase IV.
5,6) After that, it has been reported that SCR7 cyclizes automatically due to its instability, and is autoxidized to give SCR7 pyrazine. The SCR7 pyrazine inhibits NHEJ
in vitro although its selectivity to DNA ligase IV is not so high.
7,8)