Dynamics of relative chromosome position during the cell cycle.

The position of chromosomal neighborhoods in living cells was followed using three different methods for marking chromosomal domains occupying arbitrary locations in the nucleus; photobleaching of GFP-labeled histone H2B, local UV-marked DNA, and photobleaching of fluorescently labeled DNA. All methods revealed that global chromosomal organization can be reestablished through one cell division from mother to daughters. By simultaneously monitoring cell cycle stage in the cells in which relative chromosomal domain positions were tracked, we observed that chromosomal neighborhood organization is apparently lost in the early G1 phase of the cell cycle. However, the daughter cells eventually regain the general chromosomal organization pattern of their mothers, suggesting an active mechanism could be at play to reestablish chromosomal neighborhoods.