Bookmarking genes for activation in condensed mitotic chromosomes.

A hallmark feature of mitosis is the extinction of bulk cellular transcription. The mechanism by which transcription is abrogated is likely linked to mitotic specific events such as chromosome condensation. Recent studies that probe the structure of genes that can be reactivated rapidly after mitotic repression (early G1) suggest that there are structural distortions in the promoter regions of these genes. These distortions are absent in genes that are typically repressed or reactivated in later phases of the cell cycle (late G1, S, or G2). Such changes in the chromatin structure of these genes may create a transient window for transcription factor binding and rapid reactivation of genes in subsequent phases of the cell cycle.