Chromatin Takes on Liquid-Like Properties in the Living Cell

Combining several different research techniques, a group led by scientists at Japan's National Institute of Genetics has shown that chromatin forms condensed liquid-like domains in living cells but behaves like a solid at the chromosome levels. The findings, which appear this week in Science Advances, offer a new physical view of chromatin domains in active euchromatin regions. Despite advances in the understanding of chromatin activity and organization in living cells, the physical characteristics of chromatin remain unclear. The researchers used genomics, single-nucleosome imaging, and computational modeling to show that within the chromatin domain, chromatin behaves like a viscous liquid, allowing smaller proteins such as transcription factors to access the target sequences even though chromatin forms condensed domains. "This can increase chromatin accessibility and facilitate DNA transaction reactions such as RNA transcription and DNA replication/repair," the study's authors write. On the other hand, at a chromosome scale, chromatin seems to behave like a solid, likely because of many local constraints, which contribute to genome integrity. The findings, they state, strengthen the viscoelastic principle of chromatin: chromatin is locally dynamic and reactive but globally stable.