Silencing PURPL RNA Reverses Cellular Aging Through Epigenetic Reprogramming

Cellular senescence—the irreversible growth arrest of cells—is a central driver of biological aging and age-related diseases. Epigenetic changes, particularly loss of the repressive histone mark H3K9me3, are hallmarks of the senescent state, yet the upstream regulators orchestrating these changes have remained poorly understood. This study sought to fill that gap by systematically identifying long non-coding RNAs (lncRNAs) that govern senescence through epigenetic mechanisms.

The researchers profiled lncRNA expression across multiple passages of human skin fibroblasts (BJ cells) and human embryonic lung fibroblasts (IMR-90) undergoing replicative senescence, as well as in doxorubicin-induced senescence models. K-means clustering of non-coding RNA expression revealed PURPL as a consistently upregulated lncRNA during aging. Subcellular fractionation confirmed that PURPL localizes predominantly to the nucleus, implicating it in chromatin regulation.

To test PURPL's causal role, the team used CRISPRi (dCas9-ZIM3-KRAB) to transcriptionally silence PURPL in late-passage senescent cells. The results were striking: PURPL-depleted cells reverted to a morphologically younger state, showed dramatically reduced SA-β-gal staining, and downregulated canonical senescence markers including p21, p16, and loss of lamin B1 was reversed. RNA-seq confirmed a broad shift in the transcriptome toward a youthful gene expression profile. Conversely, lentiviral overexpression of PURPL in young cells accelerated the onset of senescence, recapitulating aging hallmarks.

ChIP-sequencing for H3K9me3 revealed that PURPL depletion restored this repressive histone mark at 411 genomic loci that had lost it during senescence. Key targets included SERPINE1 (encoding PAI-1, a pro-fibrotic, pro-senescence factor) and EGR1 (an early growth response transcription factor linked to senescence signaling). Loss of H3K9me3 at these loci in normal aging derepresses their transcription, establishing a feed-forward pro-senescence gene program. PURPL appears to act as a scaffold or recruiter that normally maintains this silencing, and its upregulation during aging paradoxically disrupts the repressive chromatin state at these targets.

These findings establish PURPL as a novel epigenetic gatekeeper of cellular aging with clear therapeutic implications. RNA-targeting strategies such as antisense oligonucleotides (ASOs) or CRISPRi could suppress PURPL activity to promote rejuvenation without the oncogenic or identity-loss risks associated with Yamanaka factor reprogramming. The study represents a conceptual advance by demonstrating that a single lncRNA can coordinate a broad epigenetic rejuvenation program, opening a new avenue for precision anti-aging interventions.