Cell-cycle-resolved Hi-C reveals unexpected plasticity of A/B compartments across interphase.

A/B chromatin compartments in mouse embryonic stem cells show a sudden increase in strength during S-phase, indicating unexpected plasticity across interphase.

• Why it matters: Understanding chromatin organization during the cell cycle is crucial for insights into genome regulation, yet the dynamics of A/B compartments during interphase remain poorly characterized, especially outside of mitosis.
• What they did: Using a drug-free approach combining Fucci cell-cycle indicator with in situ Hi-C, the study analyzed A/B compartment dynamics throughout interphase in mESCs, revealing a sharp increase in compartment strength at S-phase entry.
• The result: This compartment maturation involved architectural remodeling within the A compartment and was observed across developmental contexts, suggesting a revised model of nuclear organization with a critical role for the G1/S transition.