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

A/B chromatin compartments in mouse embryonic stem cells undergo a rapid, G1/S transition-dependent maturation during interphase, revealing unexpected plasticity across cell cycle stages.

• Why it matters: Understanding chromatin organization dynamics is essential for insights into genome regulation, yet the behavior of A/B compartments during interphase remains poorly characterized, especially outside of mitosis.
• What they did: Using a drug-free, combined Fucci and in situ Hi-C approach, the study analyzed A/B compartment changes throughout interphase in mESCs, focusing on the G1/S transition and S-phase.
• The result: Compartment strength increases abruptly at S-phase entry, stabilizes during S-phase, then declines, indicating a stepwise, plastic reorganization process that extends across developmental contexts and refines models of nuclear architecture.