AID accesses the genome during mitosis, cytokinesis, and a short time period in the early phase of G1. (A) Subcellular localization of AID-EGFP from mitosis to G1. AID-EGFP (green) and Lamin B (red, nuclear envelope) are represented by single optical slices (35–40 z-slices each cell). A projection of all slices of α-tubulin shows the microtubule network. The combination of nuclear envelope and microtubule network allows determination of the cell cycle stage. Bar, 10 µm. Three independent experiments. (B) Time-lapse imaging of AID-EGFP–expressing B cells during cell division (see Video 1). Single optical z-slices are shown for each time point (indicated in minutes in the top left corner). Bar, 10 µm. Two independent experiments were performed. (C) Relative fluorescence intensity of AID-EGFP after cell division. Total AID-EGFP fluorescence was measured over time, and no significant changes in total fluorescence are recorded in the daughter cells (red and blue lines).