Lamin A/C restrains replication domain activity through higher-order chromatin structures and PCNA interaction [CUT&Tag]

Lamin A/C, a critical nuclear lamina protein, is essential for maintaining nuclear architecture, organizing chromatin and preserving genomic stability. However, its role in directly regulating DNA replication remains unclear. This study investigates how Lamin A/C orchestrates replication initiation by modulating chromatin structure and interacting with proliferating cell nuclear antigen (PCNA). Utilizing high-resolution imaging, chromatin accessibility assays, and sequencing, we demonstrate that Lamin A/C stabilizes replication domains (RDs) by restricting chromatin mobility, preserving spatial organization, and maintaining accessibility. Furthermore, Lamin A/C interacts with PCNA via its Ig-fold domain, regulating PCNA availability by sequestering a pool of PCNA and modulating its expression, and thereby controlling its recruitment to replication machinery. The loss of Lamin A/C results in chromatin architecture reorganization and elevated PCNA availability at RDs, which coordinately trigger excessive activation of replication origins, leading to replication stress and DNA damage. These disruptions prolong the S phase and compromise genome stability, highlighting Lamin A/C as a critical gatekeeper of balanced replication initiation. Our findings reveal Lamin A/C’s dual role in chromatin organization and replication machinery regulation, offering valuable insights into its involvement in replication-associated diseases such as cancer and viral infections and highlighting potential therapeutic opportunities through targeting replication dynamics.