The consequences of differential origin licensing dynamics in distinct chromatin environments.

In this study the authors have, for the first time, quantified DNA replication origin licensing dynamics and distribution in single cells at subnuclear resolution. The cell cycle and DNA replication fields have long appreciated that origin licensing is both absolutely essential for replication and that licensing is strictly confined to G1 phase. The biochemical process of origin licensing- which is the DNA loading of MCM complexes- is known in considerable detail. What has never been explored in any system, is the dynamics of origin licensing itself. Here the authors define the dynamics of human MCM loading at different times within G1 in both euchromatin and heterochromatin, and explore the consequences of those dynamics for genome stability.