Figure 7.

A model for chromatin dynamics during replication and repair in mouse chromocenters.

The upper part shows the sequential steps of a heterochromatin domain (chromocenter) replication. Chromatin is duplicated by the sequential assembly of DNA replication complexes along the chromosome fiber fold. Replication of chromatin in the inner parts of the chromocenter occurs locally, which leads to decompaction of the chromatin at the sites of DNA synthesis. Translocation/rearrangements of the template and nascent DNA take place at the subdomain scales, which may correspond to chromatin loops/replicons. The bottom part shows chromatin decompaction at the site of laser-induced DNA damage. Unlike DNA replication, damaged sites that are engaged in DNA repair induced processive DNA synthesis are randomly affected by the laser beam and may localize at significant distances along the chromosome. Simultaneous processing of the damaged sites leads to the formation of ‘DNA synthesis compartment’ within the chromocenter and the corresponding increase in its overall volume.