Gene positioning relative to the nuclear architecture. (A) Anti-NPC protein antibody (MAb414) was used to visualize the nuclear membrane (top). Alternatively, a NPC subunit (Nup61) fused to a Flag epitope was expressed from the endogenous locus with its own promoter, and Nup61-Flag proteins were visualized by an IF approach (bottom). In the same cells, centromeres were covisualized by FISH (red). (B) NPC signals are used to trace the nuclear membrane, and the nucleus is divided into the three zones based on distance from the membrane. (C) The distance between the centromeric signal and the nuclear membrane was measured in more than 100 cells, and assigned to one of the nuclear zones.