Lamin A/C maintains genome topology and regulates transcriptional programs essential for virus-driven B cell activation.

Lamin A/C is a crucial structural component of the nuclear lamina that influences chromatin organization and gene regulation. In this study, we demonstrate that lamin A/C is vital for maintaining higher-order genome organization and transcriptional programs that support EBV-driven B-cell activation. Loss of lamin A/C in a B-lymphoblastoid cell line caused significant three-dimensional reorganization of the genome, evidenced by the loss of long-range chromatin loops, an increase in short-range contacts, and redistribution of H3K9me2- marked heterochromatin. These structural disruptions were linked to widespread changes in gene expression affecting metabolic, signaling, and differentiation pathways. Mechanistically, lamin A/C influences the nuclear positioning and transcription of CTCF-bound loci by preventing their relocation to the periphery and their association with lamin B1. Blocking H3K9me2 deposition mimicked the transcriptional effects of lamin A/C depletion and revealed increased sensitivity to PI3K inhibitors. Overall, our results identify lamin A/C as a key organizer of genome structure and epigenetic regulation in EBV-infected B cells, uncovering a lamin-dependent pathway that connects nuclear architecture, metabolism, and viral disease processes.