Senescence-Associated Chromatin Rewiring Promotes Inflammation and Transposable Element Activation.

Cellular senescence is a stable form of cell cycle arrest that contributes to aging and age-associated diseases through the secretion of inflammatory factors collectively known as the senescence-associated secretory phenotype (SASP). While senescence is driven by transcriptional and epigenetic changes, the contribution of higher-order genome organization remains poorly defined. Here, we present the highest-resolution Hi-C maps (~3 kb) to date of proliferating, quiescent, and replicative senescent (RS) human fibroblasts, enabling a comprehensive analysis of 3D genome architecture during senescence. Our analyses reveal widespread senescence-associated remodeling of chromatin architecture, including extensive compartment and subcompartment switching toward transcriptionally active states, and a dramatic increase in unique chromatin loops. These structural features correlate with local DNA hypomethylation and are largely independent of canonical CTCF binding. The altered 3D genome landscape supports expression of SASP genes, inflammation-related pathways, and neuronal gene signatures consistent with age-associated epigenetic drift. We further demonstrate that architectural changes at multiple levels, including compartments, subcompartments, and loops, facilitate the derepression of LINE-1 retrotransposons, linking 3D chromatin structure to activation of proinflammatory transposable elements. Interestingly, quiescent cells, commonly used as senescence controls, exhibited substantial overlap in inflammatory gene expression with senescent cells, raising important considerations for experimental design. Structural analysis of cell cycle genes showed distinct chromatin configurations in senescence versus quiescence, despite similar transcriptional repression. Together, our results establish a high-resolution framework for understanding how genome architecture contributes to the senescent state.