Super-resolution imaging reveals that cohesin prevents local mixing of compact, active genome domains
The human genome is about two meters (6.6 feet) long, yet it is folded inside a cell nucleus only about 10 micrometers in diameter. To fit into this tiny space, DNA is wrapped around histone proteins to form nucleosomes, which are further organized into chromatin. For decades, chromatin has often been described in two simple forms: euchromatin, which is active, open and accessible, and…
A recent study published in Nature Genetics on September 8, 2026, reveals that cohesin, a protein complex, prevents local mixing of condensed euchromatic domains in living human cells. Euchromatin, previously thought to be merely open and accessible, can actually form condensed, dynamic domains. Removing cohesin increases nucleosome mobility within these domains, causing them to mix more locally without changing overall chromatin compaction.
This local mixing weakens transcriptional insulation, making genes in adjacent domains more likely to be activated together. Euchromatin is thus better understood as a collection of condensed, dynamic, and functionally insulated domains controlled by cohesin. Cohesin dysfunction, linked to developmental disorders and cancer, may provide new insights into genome regulation failures in disease.
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