Fibroblasts of a healthy control and RS-SCID patients with mutations in the Artemis gene show equal usage of direct joining and microhomology when rejoining linearized DNA constructs.

(A) Linearized DNA constructs with homologous ends (ATCAGC) can be rejoined via direct joining or via microhomology. Joining via microhomology results in the generation of a BstXI restriction site (CCAN₆TGG). (B) In contrast to normal fibroblasts and fibroblasts from patients with an Artemismutation, fibroblasts with a mutation in DNA ligase IV (180BR) show complete absence of direct joining and full usage of the microhomology pathway.