Regulatory machinery is focally organized in the interphase nucleus.

The information contained in these focal nuclear microenvironments must be inherited during cell division to sustain physiologically responsive gene expression in progeny cells.

Focal mitotic retention of phenotypic transcription factors at promoters together with histone modifications and DNA methylation—a mechanism collectively known as gene bookmarking— is a novel parameter of inherited epigenetic control that sustains cellular identity after mitosis.

The epigenetic signatures imposed by bookmarking poise genes for activation or suppression following mitosis.

References

 Mitotic bookmarking of genes: a novel dimension to epigenetic control. Zaidi SK, Young DW, Montecino MA, Lian JB, van Wijnen AJ, Stein JL, Stein GS. Nat Rev Genet. 2010 Aug;11(8):583-9. PMID: 20628351