Lamin A/C restrains replication domain activity through higher-order chromatin structures and PCNA interaction [ATAC-Seq]

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. Overall design: ATAC-seq of wild-type (WT) and Lamin A/C knockout Hela cells during G1/S phase.

核纤层蛋白Lamin A/C是一类关键核纤层蛋白，对于维持细胞核架构、组织染色质结构以及保障基因组稳定性至关重要。然而，其直接调控DNA复制的具体作用机制仍未明确。本研究围绕Lamin A/C如何通过调控染色质结构、与增殖细胞核抗原（proliferating cell nuclear antigen，PCNA）相互作用，进而协调复制起始过程展开探究。
研究团队采用高分辨率成像、染色质可及性检测及测序技术，证实Lamin A/C可通过限制染色质流动性、维持空间组织状态并保持染色质可及性，从而稳定复制结构域（replication domains，RDs）。进一步研究发现，Lamin A/C可通过其Ig折叠结构域（Ig-fold domain）与PCNA结合，通过隔离特定PCNA库并调控其表达水平来调节PCNA的可用性，进而控制PCNA向复制机器的招募过程。
Lamin A/C的缺失会引发染色质结构重编程，并提升复制结构域处的PCNA可用性，二者协同触发复制原点的过度激活，最终导致复制应激与DNA损伤。此类破坏会延长细胞S期进程并损害基因组稳定性，凸显Lamin A/C作为平衡复制起始的关键守门因子。本研究揭示了Lamin A/C在染色质组织与复制机器调控中的双重作用，为其参与癌症、病毒感染等复制相关疾病的机制提供了全新见解，并指出通过靶向复制动态过程的潜在治疗机遇。
整体实验设计：G1/S期野生型（WT）与Lamin A/C敲除HeLa细胞的ATAC-seq测序分析。