SeneSIQ›Mechanism
Mechanism

p21CIP1 (CDKN1A)

Reference definition for a cellular-senescence node.

Arrest effector

Definition

Category: Arrest effector

Also known as: p21, CDKN1A, WAF1

A p53-transcribed cyclin-dependent kinase inhibitor that enforces the early, sometimes reversible phase of cell-cycle arrest. p21 acts upstream of and in parallel with p16 in establishing senescence, particularly in response to DNA damage.

Key points

  • p21 is induced rapidly after genotoxic stress via the p53 pathway.
  • It is one of the biomarkers measured in human senolytic pilots (e.g. adipose-tissue p21 in the diabetic-kidney-disease study).
  • Sustained p21 and p16 together mark the transition to stable senescence.

Related interventions

Sourcing

Standard senescence reviews; measured in Hickson et al. 2019.

Reference synthesis (tier 4); verification: review_level_2026-07-12.