Targeting the locus to the nuclear lamina requires passage through mitosis. (A) G1/S-phase block using hydroxyurea in targeting cell line from day 0 (D0) to day 3.5 (D3.5). (B) Representative images of LacI-mCherry–Lamin B1–expressing cells used for counting to quantify G1/S-blocked nontargeted (a, red, arrow) and targeted (b, red, arrow) cells and asynchronous nontargeted (c, red, arrow) and targeted (d, red, arrow) cells. Bar, 5 μm. (C) Quantification of the percentage of nontargeted and targeted cells in G1/S-blocked and asynchronous cells. The graphical data represents the mean and standard deviation of three experiment (n = 100 nuclei per experiment). Approximately 10% of the cells did not exhibit a nuclear mCherry signal. (D) Still images (a–o) from time series (0–90 min, G2 to early G1 phase) of targeting clone H2A-YFP going through mitosis. Targeting cells stably expressing histone H2A-YFP (green) were induced to express LacI-mCherry–Lamin B1 (red, arrow). Images are projections of deconvolved z stacks taken after every 10 min. Bar, 5 μm. See video 1 for the entire time series.