A3G-mediated DSB repair is cytidine deaminase dependent. (A) Immunoblot of A3G in SupT11 cells stably expressing an EV control, wild-type A3G, or A3G E259Q catalytic mutant. α-tubulin was used as a loading control. (B) Quantification of γ-H2AX foci in SupT11 cells 24 hours after IR (4 Gy). Values represent mean ± SD from 2 independent experiments and at least 10 different fields. (C) H9 cells were incubated for 2 hours with the indicated Vif-derived peptides, irradiated (4 Gy) or mock-irradiated (No IR), and stained after 8 hours with anti-A3G and anti–γ-H2AX antibodies. Nuclei were counterstained with DAPI. (Bottom) Values represent mean ± SD from 2 independent experiments and at least 10 different fields. (Inset) Magnification of an irradiated cell preincubated with Vif25-39.