Localization of ATM protein at various cell cycle phases. Cells were synchronized at various cell cycle phases and processed for immunofluorescence with affinity-purified pAb 132 (a, c, e, and g) and Hoechst 22358 (b, d, f, and h). (a and b) Cells synchronized at G0. (c and d) Cells synchronized at G1. (e and f) Cells synchronized at G1/S. (g and h) Cells synchronized in mitosis.