Artemis overexpression in K562 leads to a decrease in large deletions. (A) Western blotting in K562 cells transfected with the myc-tagged Artemis cDNA construct (pcDNA huASC1D) showing Artemis overexpression. Ku86 was used as loading control. An in vivo LacZα plasmid reactivation assay was used to measure end joining in Artemis overexpressed cells, compared with empty vector–transfected controls. (B) Relative percentage of colonies, indicating the efficiency of end joining. (C) Graph of percentage of large deletions, defined as more than 20 bp. (D) Agarose gel showing PCR products of repaired colonies in empty vector controls and Artemis overexpressed K562 cells. (E) The percentage of plasmids repaired using DNA sequence microhomologies of 1 to 6 bp. Fifteen plasmids were sequenced. Values significantly different are marked with an asterisk (Student t test; P < .001 for panels C and E). Error bars reflect the standard error of the mean.