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Dietary and genetic effects on age-related loss of gene silencing reveal epigenetic plasticity of chromatin repression during aging.

ABSTRACT: During aging, changes in chromatin state that alter gene transcription have been postulated to result in expression of genes that are normally silenced, leading to deleterious age-related effects on cellular physiology. Despite the prevalence of this hypothesis, it is primarily in yeast that loss of gene silencing with age has been well documented. We use a novel position effect variegation (PEV) reporter in Drosophila melanogaster to show that age-related loss of repressive heterochromatin is associated with loss of gene silencing in metazoans and is affected by Sir2, as it is in yeast. The life span-extending intervention, calorie restriction (CR), delays the age-related loss of gene silencing, indicating that loss of gene silencing is a component of normal aging. Diet switch experiments show that such flies undergo a rapid change in their level of gene silencing, demonstrating the epigenetic plasticity of chromatin during aging and highlighting the potential role of diet and metabolism in chromatin maintenance, Thus, diet and related interventions may be of therapeutic importance for age-related diseases, such as cancer.

SUBMITTER: Jiang N

PROVIDER: S-EPMC3868724 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Dietary and genetic effects on age-related loss of gene silencing reveal epigenetic plasticity of chromatin repression during aging.

Jiang Nan N Du Guyu G Tobias Ethan E Wood Jason G JG Whitaker Rachel R Neretti Nicola N Helfand Stephen L SL

Aging 20131101 11

During aging, changes in chromatin state that alter gene transcription have been postulated to result in expression of genes that are normally silenced, leading to deleterious age-related effects on cellular physiology. Despite the prevalence of this hypothesis, it is primarily in yeast that loss of gene silencing with age has been well documented. We use a novel position effect variegation (PEV) reporter in Drosophila melanogaster to show that age-related loss of repressive heterochromatin is a ...[more]

PMID: 24243774

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Project description:FOXA1 expression correlates with the breast cancer luminal subtype and patient survival. RNA and protein analysis of a panel of breast cancer cell lines revealed that BRCA1 deficiency is associated with the downregulation of FOXA1 expression. Knockdown of BRCA1 resulted in the downregulation of FOXA1 expression and enhancement of FOXA1 promoter methylation in MCF-7 breast cancer cells, whereas the reconstitution of BRCA1 in Brca1-deficent mouse mammary epithelial cells (MMECs) promoted Foxa1 expression and methylation. These data suggest that BRCA1 suppresses FOXA1 hypermethylation and silencing. Consistently, the treatment of MMECs with the DNA methylation inhibitor 5-aza-2'-deoxycitydine induced Foxa1 mRNA expression. Furthermore, treatment with GSK126, an inhibitor of EZH2 methyltransferase activity, induced FOXA1 expression in BRCA1-deficient but not in BRCA1-reconstituted MMECs. Likewise, the depletion of EZH2 by small interfering RNA enhanced FOXA1 mRNA expression. Chromatin immunoprecipitation (ChIP) analysis demonstrated that BRCA1, EZH2, DNA methyltransferases (DNMT)1/3a/3b and H3K27me3 are recruited to the endogenous FOXA1 promoter, further supporting the hypothesis that these proteins interact to modulate FOXA1 methylation and repression. Further co-immunoprecipitation and ChIP analysis showed that both BRCA1 and DNMT3b form complexes with EZH2 but not with each other, consistent with the notion that BRCA1 binds to EZH2 and negatively regulates its methyltransferase activity. We also found that EZH2 promotes and BRCA1 impairs the deposit of the gene silencing histone mark H3K27me3 on the FOXA1 promoter. These associations were validated in a familial breast cancer patient cohort. Integrated analysis of the global gene methylation and expression profiles of a set of 33 familial breast tumours revealed that FOXA1 promoter methylation is inversely correlated with the transcriptional expression of FOXA1 and that BRCA1 mutation breast cancer is significantly associated with FOXA1 methylation and downregulation of FOXA1 expression, providing physiological evidence to our findings that FOXA1 expression is regulated by methylation and chromatin silencing and that BRCA1 maintains FOXA1 expression through suppressing FOXA1 gene methylation in breast cancer.

Dataset Information

Dietary and genetic effects on age-related loss of gene silencing reveal epigenetic plasticity of chromatin repression during aging.

Publications

Dietary and genetic effects on age-related loss of gene silencing reveal epigenetic plasticity of chromatin repression during aging.

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