FoxO-dependent and -independent mechanisms mediate SirT1 effects on IGFBP-1 gene expression
- 作者：Lixia Gan ; Yingshan Han ; Stephane Bastianetto ; Yvan Dumont ; Terry G. Unterman and Remi Quirion
- 关键词：IGFBP-1 ; SirT1 ; FoxO1 ; Gene expression ; Mitogen-activated protein kinase pathway
- 刊名：Biochemical and Biophysical Research Communications
- 出版年：2005
- 期刊代码：159_0006291x
- 类别：bio
- 出版时间：2005
- 卷：337
- 期：4
- 页码：1092-1096
- 文件大小：197 K
摘要
Sirtuin 1 (SirT1), an NAD-dependent deacetylase that is important for promoting longevity during caloric restriction, can deacetylate and enhance the function of forkhead box transcription factors, O subfamily (FoxO). We examined the effect of SirT1 on the regulation of insulin-like growth factor-binding protein 1 (IGFBP-1), a known target of FoxO proteins that is increased in fasting. Co-transfection with a SirT1 expression vector dose-dependently stimulated IGFBP-1 promoter activity and a heterologous reporter gene construct containing three FoxO-binding sites linked to a minimal promoter. This effect is mimicked by 20 μM resveratrol, a potent SirT1 activator, and immunoprecipitation and Western blotting confirm that SirT1 and FoxO1 interact in cells. Interestingly, mutation of FoxO-binding sites in the IGFBP-1 promoter reduces, but does not completely disrupt, the stimulatory effect of SirT1 on promoter activity. We found that overexpression of SirT1 is accompanied by enhanced mitogen-activated protein kinase (MAPK) activation. Treatment of SirT1-cotransfected cells with PD98059, which inhibits MAPK activation, decreased IGFBP-1 promoter activity by 
50%, in a FoxO-binding site-independent manner, and disrupts the residual effect of SirT1. These results indicate that SirT1 stimulates IGFBP-1 promoter activity through FoxO-dependent and -independent mechanisms, and provides the first evidence that activation of MAPK contributes to effects of SirT1 on gene expression.
50%, in a FoxO-binding site-independent manner, and disrupts the residual effect of SirT1. These results indicate that SirT1 stimulates IGFBP-1 promoter activity through FoxO-dependent and -independent mechanisms, and provides the first evidence that activation of MAPK contributes to effects of SirT1 on gene expression.