Large-Scale Clustered Transcriptional Silencing Associated With Cellular Senescence

Senescence is a cell fate associated with age-related pathologies; however, senescence markers are not well-defined. Using single cell multi-isotope imaging mass spectrometry (MIMS), we identified hypercondensed, transcriptionally silent DNA globules in a senescence model induced by dysfunctional telomeres. This architectural phenomenon was associated with geographically clustered transcriptional repression across somatic chromosomes with over-representation of cell cycle genes. Senescence-stimuli was associated with a higher frequency of cells that exhibited geographically concentrated transcriptional repression relative to control cells. This phenomenon was also observed in multiple other senescence models, including replicative senescence and irradiation. We further identified an enrichment of common pathways in all models of senescence, suggesting a common cellular response to this silencing phenomenon. Such large-scale clustered silencing of chromosomal segments rather than individual genes may explain senescence heterogeneity and a putative trajectory toward deep, irreversible senescence.