Inhibition of p21-mediated ROS accumulation can rescue p21-induced senescence.
The cyclin-dependent kinase (CDK) inhibitor p21(Waf1/Cip1/Sdi1) was identified initially as a gene induced in senescent cells and itself has been shown to cause permanent growth arrest/senescence. Reactive oxygen species (ROS), a byproduct of oxidative processes, can also induce an irreversible growth arrest similar to senescence. Here we show that p21 increased intracellular levels of ROS both in normal fibroblasts and in p53-negative cancer cells. N-acetyl-L-cysteine, an ROS inhibitor, rescued p21-induced senescence, showing that ROS elevation is necessary for induction of the permanent growth arrest phenotype. p16(Ink4a), a CDK4- and CDK6-specific inhibitor, failed to increase ROS levels, and cell cycle arrest induced by p16 was reversible following its down-regulation, demonstrating the specificity of this p21 effect. A p21 mutant that lacked the ability to bind proliferating cell nuclear antigen (PCNA) retained the ability to induce both ROS and permanent growth arrest. All of these findings establish that p21 mediates senescence by a mechanism involving ROS accumulation which does not require either its PCNA binding or the CDK inhibitory functions shared with p16.
Macip
Salvador
S
Derald H.Ruttenberg Cancer Center, Mount Sinai School of Medicine, One Gustave L.Levy Place, Box 1130, New York, NY 10029, USA.
Igarashi
Makoto
M
Fang
Li
L
Chen
Angus
A
Pan
Zhen-Qiang
ZQ
Lee
Sam W
SW
Aaronson
Stuart A
SA
D000111:Acetylcysteine / Q000494:pharmacology; D016922:Cellular Senescence / Q000502:physiology*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology; D016166:Free Radical Scavengers / Q000494:pharmacology; D006801:Humans; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014407:Tumor Cells, Cultured
C493956:CDKN1A protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D016166:Free Radical Scavengers; D018809:Proliferating Cell Nuclear Antigen; D017382:Reactive Oxygen Species; D000111:Acetylcysteine