Repair analysis after MSI1 alterations. A: Schematic representation of vector EJ5-GFP, which is designed to measure frequency of total end-joining events. Expression of ISceI introduces double-strand breaks at corresponding recognition sites, excision of the intervening puro cassette, and restoration of functional Green fluorescent protein (GFP) gene. B: Analysis of change in end-joining frequency with MSI1 knockdown and DNA–PKcs overexpression in the absence of MSI1 using EJ5-GFP assay. Data are presented as means ± SD. n = 3 (B). ∗∗P < 0.01. Ctrl, control; si, small interfering.