Cohesin prevents local mixing of condensed euchromatic domains in living human cells.

Cohesin maintains the integrity of condensed euchromatic domains in living human cells, preventing local mixing and preserving gene regulation.

• Why it matters: Understanding how cohesin organizes active euchromatin is crucial because it influences transcription and DNA repair processes, yet its precise role in living cells remains unclear.
• What they did: The study used single-nucleosome imaging, super-resolution microscopy, and euchromatin-specific labeling to observe chromatin organization, revealing that cohesin constrains euchromatin into condensed domains.
• The result: Loss of cohesin increased nucleosome fluidity within these domains, causing local mixing and disrupting transcriptional insulation, which highlights cohesin’s physical role in gene expression regulation.