Contribution of p16(INK4a) to replicative senescence of human fibroblasts.
In standard conditions of tissue culture, human fibroblasts undergo a limited number of population doublings before entering a state of irreversible growth arrest termed replicative senescence or M1. The arrest is triggered by a combination of telomere dysfunction and the stresses inflicted by culture conditions and is implemented, at least in part, by the cyclin-dependent kinase inhibitors p21(CIP1) and p16(INK4a). To investigate the role of p16(INK4a), we have studied fibroblasts from members of melanoma prone kindreds with mutations in one or both copies of the CDKN2A locus. The mutations affect the function of p16(INK4a) but not of the alternative product, p14(ARF). The p16(INK4a)-defective fibroblasts have an above average life span, compared to the heterozygous and normal age-matched controls, but they arrest with characteristics typical of senescence. Using agents that are known to bypass M1, such as DNA tumor virus oncoproteins or the Bmi1 transcriptional repressor, we provide evidence that p16(INK4a) defective cells arrest at a stage that is operationally between M1 and M2 (crisis). As well as indicating that p16(INK4a) contributes to but is not essential for replicative senescence of human fibroblasts, our data reveal considerable heterogeneity in the levels and accumulation of p16(INK4a) in different strains.
Brookes
Sharon
S
Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London WC2A 3PX, UK.
Rowe
Janice
J
Gutierrez Del Arroyo
Ana
A
Bond
Jane
J
Peters
Gordon
G
D002453:Cell Cycle / Q000235:genetics*; D002460:Cell Line; D002470:Cell Survival / Q000235:genetics; D016922:Cellular Senescence / Q000235:genetics*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D019942:Genes, p16 / Q000502:physiology; D006801:Humans; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D063150:Polycomb Repressive Complex 1; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism
C069077:BMI1 protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D025803:Tumor Suppressor Protein p14ARF; D063150:Polycomb Repressive Complex 1