Submolecular-Resolution 3D Dynamics of Heterochromatin Formation

Heterochromatin is a physical state of the chromatin fiber that maintains gene repression during cell development. Although evidence exists on molecular mechanisms involved in heterochromatin formation, a detailed structural mechanism of heterochromatin formation needs a better understanding. We made use of a simple simulation model with explicit representation of key molecular events, to observe molecular self-organization leading to heterochromatin formation. This simple unbiased simulation provides a comprehensive structural interpretation of micro- and macroscopic heterochromatin properties. In particular, this study suggests a structural mechanism by which chromatin bridging potentially promotes formation of condensed chromatin. It also elucidates the structural roots of a yet poorly understood phenomenon of a non-deterministic nature of heterochromatin formation and subsequent gene repression. Experimental Chromatin in vivo Assay provided an unbiased estimate of time scale of repressive response to a heterochromatin-triggering event.