C and D, Knockdown of POLD3 impairs RMD when a DSB is close to one repeat. RMD frequency was determined in U2OS (EGFP-SSA-3427-17) cells using the indicated sgRNAs/Cas9 with or without depletion of POLD3 by lentivirus-expressed shRNA. Cells infected with a lentiviral empty vector were used as control. The distance between the sgRNA/Cas9 cleavage sites and the repeat sequences is indicated. The knockdown level of POLD3 was shown by Western blot, and KU70 was used as the loading control. 