GSE128487
SirT7 auto-ADPribosylation regulates glucose starvation response through macroH2A1.1 (ChIP-seq)
Sirtuins are key players in the response to oxidative, metabolic and genotoxic stress, and are involved in genome stability, metabolic homeostasis and aging. Originally described as NAD+-dependent deacetylases, some sirtuins are also characterized by poorly understood mono-ADP-ribosyltransferase (MADPRT) activity. Here we report that the deacetylase SirT7 is a dual sirtuin as it also features auto-MADPRT activity. Molecular and structural evidence suggests that this novel activity occurs at a second previously undefined active site that is physically separated in another domain. Specific abrogation of this activity alters SirT7 chromatin distribution, suggesting a role for this modification in SirT7 chromatin binding specificity and localization. Our studies uncover an epigenetic pathway by which ADP-ribosyl-SirT7 is recognized by the ADP-ribose reader macroH2A1.1, a histone variant involved in chromatin organization, metabolism and differentiation. Glucose starvation (GS) boosts this interaction and promotes SirT7 re-localization intergenic regions in a macroH2A1-dependent manner, which is required for specific up- or downregulation of a subset of nearby genes upon GS in primary cells and in vivo in the livers of calorie-restricted (CR) Wt and SirT7-/- mice. The level of expression of these genes decreases with age in SirT7-deficient mice, reinforcing the link between Sirtuins, CR and aging. Our work provides a novel perspective about sirtuin duality and suggests a key role for SirT7/macroH2A1.1 axis in mammalian glucose homeostasis, calorie restriction signaling and aging. Overall design: Chromatin from 14.5 day WT and SirT7-/- MEFs was subjected to ChIP using antibodies raised against SIRT7, macroH2A1.1, and H3K27me3, and subjected to high-throughput sequencing.