Circadian Gating of p21-Mediated Quiescence as a Safeguard Against Geroconversion: A Mechanistic Hypothesis

Cellular senescence is a major driver of tissue aging, yet the molecular conditions that determine whether a cell undergoing p21-mediated arrest enters reversible quiescence versus irreversible senescence remain incompletely understood. We propose that the circadian clock creates a physiological time window, defined by BMAL1-driven suppression of mTORC1, in which p21-mediated cell cycle arrest leads to quiescence rather than geroconversion. We term this process circadian gating of quiescence (CGQ). The hypothesis integrates three independently established findings and presents two testable predictions with a minimal experimental protocol. If confirmed, this framework reframes circadian disruption as a contributing mechanism of senescence accumulation and points toward temporal coordination of cell cycle checkpoints as a potential target for anti-aging intervention.