New insights on chromatin organization

Along the research line on the structural properties of chromatin, members of CC&B lead by Guido Tiana have recently published an article on Biophysical Journal focused on the conformational fluctuations of interphasic chromatin. The dynamics of the chromatin fibre of mouse embryonic stem cells is studied making use of a physical polymeric model based on experimental data. The result is that the chromatin fiber within TADs can easily fluctuate between several conformational states, which are hierarchically organized and are not separated by important free energy barriers, and that this is facilitated by the fact that the chromatin fiber within TADs is close to the onset of the coil-globule transition. Making use of live-cell experiments to measure the dynamics of the chromatin fiber in mouse embryonic stem cells, in combination with dynamical simulations, we predict that conformational changes within one TAD are likely to occur on timescales that are much shorter than the duration of one cell cycle. This suggests that genes and their regulatory elements may come together and disassociate several times during a cell cycle. These results have important implications for transcriptional regulation as they support the concept of highly dynamic interactions driven by a complex interplay between site-specific interactions and the intrinsic biophysical properties of the chromatin fiber.

Guido Tiana, Assaf Amitai, Tim Pollex, Tristan Piolot, David Holcman, Edith Heard, Luca Giorgetti
Structural Fluctuations of the Chromatin Fiber within Topologically Associating Domains
Biophysical Journal, 110, 1234 (2016)
http://www.cell.com/biophysj/fulltext/S0006-3495(16)00146-6