Regulation of p53 during senescence in normal human keratinocytes

Aging Cell

Reuben H. Kim¹  Mo K. Kang¹  Terresa Kim¹  Paul Yang¹  Susan Bae¹  Drake W. Williams¹  Samantha Phung¹  Ki-Hyuk Shin¹  Christine Hong¹ 

[1] UCLA School of Dentistry, Los Angeles, CA, USA

关键词: aging;    cancer;    epigenetics;    human keratinocytes;    p53;    replicative senescence;   

DOI  :  10.1111/acel.12364

来源: Wiley

【 摘 要 】

Summary

p53, the guardian of the genome, is a tumor suppressor protein and critical for the genomic integrity of the cells. Many studies have shown that intracellular level of p53 is enhanced during replicative senescence in normal fibroblasts, and the enhanced level of p53 is viewed as the cause of senescence. Here, we report that, unlike in normal fibroblasts, the level of intracellular p53 reduces during replicative senescence and oncogene-induced senescence (OIS) in normal human keratinocytes (NHKs). We found that the intracellular p53 level was also decreased in age-dependent manner in normal human epithelial tissues. Senescent NHKs exhibited an enhanced level of p16^INK4A, induced G₂ cell cycle arrest, and lowered the p53 expression and transactivation activity. We found that low level of p53 in senescent NHKs was due to reduced transcription of p53. The methylation status at the p53 promoter was not altered during senescence, but senescent NHKs exhibited notably lower level of acetylated histone 3 (H3) at the p53 promoter in comparison with rapidly proliferating cells. Moreover, p53 knockdown in rapidly proliferating NHKs resulted in the disruption of fidelity in repaired DNA. Taken together, our study demonstrates that p53 level is diminished during replicative senescence and OIS and that such diminution is associated with H3 deacetylation at the p53 promoter. The reduced intracellular p53 level in keratinocytes of the elderly could be a contributing factor for more frequent development of epithelial cancer in the elderly because of the loss of genomic integrity of cells.

【 授权许可】

CC BY   
© 2015 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

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