Gene
CDKN1A (p21)
Last updated 2026-07-02· Last reviewed 2026-07-02· 1 min read
Reviewed by the Ultimate Longevity Bible editorial team. Educational reference — not medical advice. See disclaimer.
Function
- Binds and inhibits cyclin-CDK complexes required for G1/S transition — enforces cell-cycle arrest.
- Sustained p21 expression drives senescence; transient expression enables DNA repair and re-entry into cycle.
Aging relevance
- p21-high senescent cells accumulate in aged tissues.
- Genetic p21 knockout: shortens lifespan (due to genomic instability); tissue-specific knockdown extends healthspan in some models.
- p21-directed senolytics: an active development area — molecules that selectively kill p21-high cells without affecting healthy proliferating cells.
- Rapamycin vs Senolytics — Comparison.
- Senomorphic — Concept.
- Senomorphic vs Senolytic — Concept.
- Senotherapeutic — Concept.
- p38 MAPK Stress Pathway — Pathway.