SIRT1 prevents replicative senescence of normal human umbilical cord fibroblast through potentiating the transcription of human telomerase reverse transcriptase gene.

SIRT1, the mammalian homolog of sirtuins, has emerged as a mediator of the beneficial effects of calorie restriction. Among them, we focused on the SIRT1-induced prevention of cellular senescence, and tried to reveal the molecular mechanisms that define the effects of SIRT1. Firstly in this study, we observed that overexpression of SIRT1 resulted in the prevention of cellular senescence of normal human umbilical cord fibroblast HUC-F2 cells. Here, we focused on the human telomerase reverse transcriptase (hTERT) gene as a target of the SIRT1-induced prevention of cellular senescence. Results showed that SIRT1, SIRT1 activator, resveratrol, and SIRT1 activating condition, starved condition, increased the transcription of hTERT in HUC-F2 cells. Next, we found that SIRT1 increased hTERT transcription in a c-MYC-dependent manner, triggered the transcription of the c-MYC gene and increased the amount of c-MYC recruited to the hTERT promoter. Further, SIRT1 increased the transcriptional activation ability of c-MYC and correspondingly increased the amount of acetylated H4 histone at the hTERT promoter. All of these results indicated that SIRT1 activates hTERT transcription through the involvement of c-MYC, and suggested that this SIRT1-induced augmentation of hTERT transcription resulted in the extension of the cellular life span of HUC-F2 cells.