Spontaneous DNA double-strand break formation is reduced in Rev3l complemented MEFs.

(A) DAPI staining of empty vector (EV)-expressing Rev3l+/Δ, Rev3l-/Δ, as well as Rev3l-/Δ MEFs expressing wild-type or ASM recombinant REV3L; arrows indicate micronuclei, with an enlarged example in the inset. (B) Merged immunofluorescence staining of the same MEFs as in (A) with DAPI (blue), 53BP1 (red) and γ-H2AX (green); foci indicate areas of DNA double-strand breaks. (C) Quantification of percent of nuclei that have associated micronuclei. (D) Quantification of cells with fewer than 3, 3 to 5, 6 to 10 or greater than 10 53BP1 foci (as measured using CellProfiler). The bars are color-coded exactly as in Part C to indicate the genotype of the MEFs (*) p < 0.01. Data represent mean ± SEM.