Inheritance through Mitosis
During mitosis chromatin undergoes roughly 500-fold compaction. This gross structural rearrangement is accompanied by many biochemical changes, including general transcriptional repression. These events present a potential challenge to any chromatin-based mechanism of inheritance through mitosis.
There are two types of models for how epigenetic factors, like the Polycomb Group proteins, can retain memory through mitosis. In one class of models (A) PcG proteins remain associated with the genes they regulate and thus the proteins themselves constitute the "memory." In a second class of models (B) the association of PcG proteins with their target genes is disrupted during mitosis. Inheritance of transcriptional states therefore requires that they faithfully reassociate with their targets after mitosis. This type of model may include the creation of a mark on chromatin that is stable through mitosis and is subsequently used to recruit PcG proteins to re-establish repression.
