Bimodal regulation of p21waf1 protein as function of DNA damage levels

G. Buscemi, C. Ricci, L. Zannini, E. Fontanella, P. Plevani, D. Delia

Research output: Contribution to journalArticlepeer-review


Human p21Waf1 protein is well known for being transcriptionally induced by p53 and activating the cell cycle checkpoint arrest in response to DNA breaks. Here we report that p21Waf1 protein undergoes a bimodal regulation, being upregulated in response to low doses of DNA damage but rapidly and transiently degraded in response to high doses of DNA lesions. Responsible for this degradation is the checkpoint kinase Chk1, which phosphorylates p21Waf1 on T145 and S146 residues and induces its proteasome-dependent proteolysis. The initial p21Waf1 degradation is then counteracted by the ATM-Chk2 pathway, which promotes the p53-dependent accumulation of p21Waf1 at any dose of damage. We also found that p21Waf1 ablation favors the activation of an apoptotic program to eliminate otherwise irreparable cells. These findings support a model in which in human cells a balance between ATM-Chk2-p53 and the ATR-Chk1 pathways modulates p21Waf1 protein levels in relation to cytostatic and cytotoxic doses of DNA damage.

Original languageEnglish
Pages (from-to)2901-2912
Number of pages12
JournalCell Cycle
Issue number18
Publication statusPublished - Sep 15 2014


  • Apoptosis
  • Cell survival
  • DNA damage response
  • Double strand breaks

ASJC Scopus subject areas

  • Cell Biology
  • Molecular Biology
  • Developmental Biology


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