Abstract
Upon severe DNA damage a cellular signalling network initiates a cell death response through activating tumour suppressor p53 in association with promyelocytic leukaemia (PML) nuclear bodies. The deacetylase Sirtuin 1 (SIRT1) suppresses cell death after DNA damage by antagonizing p53 acetylation. To facilitate efficient p53 acetylation, SIRT1 function needs to be restricted. How SIRT1 activity is regulated under these conditions remains largely unclear. Here we provide evidence that SIRT1 activity is limited upon severe DNA damage through phosphorylation by the DNA damage-responsive kinase HIPK2. We found that DNA damage provokes interaction of SIRT1 and HIPK2, which phosphorylates SIRT1 at Serine 682 upon lethal damage. Furthermore, upon DNA damage SIRT1 and HIPK2 colocalize at PML nuclear bodies, and PML depletion abrogates DNA damage-induced SIRT1 Ser682 phosphorylation. We show that Ser682 phosphorylation inhibits SIRT1 activity and impacts on p53 acetylation, apoptotic p53 target gene expression and cell death. Mechanistically, we found that DNA damage-induced SIRT1 Ser682 phosphorylation provokes disruption of the complex between SIRT1 and its activator AROS. Our findings indicate that phosphorylation-dependent restriction of SIRT1 activity by HIPK2 shapes the p53 response.
Highlights
We show that Sirtuin 1 (SIRT1) activity is restricted in response to severe DNA damage through phosphorylation of SIRT1 by Homeodomain interacting protein kinase 2 (HIPK2) at promyelocytic leukaemia (PML)-nuclear bodies (NBs)
SIRT1 and HIPK2 are known to localize to PML-NBs and to regulate p53 modification in response to genotoxic stress.[46]
Association of Flag-SIRT1 and GFP-HIPK2 was clearly potentiated in response to Adriamycin treatment (Figure 1b), supporting the conclusion that SIRT1–HIPK2 complex formation is stimulated by DNA damage
Summary
SIRT1 activity is regulated by various mechanisms including posttranslational modifications, intramolecular interaction as well as interaction with an inhibitor, deleted in breast cancer 1 (DBC1), or an activator, active regulator of SIRT1 (AROS).[19,20,21,22,23,24,25] Previous reports show that ATM and ATR checkpoint kinases regulate SIRT1 function through phosphorylation of DBC1 at Thr[454], which increases SIRT1-DBC1 binding.[24,25] SIRT1 is regulated in response to oxidative stress through phosphorylation at Ser[27], Ser[47] and. Tumour suppressor Homeodomain interacting protein kinase 2 (HIPK2) is a DNA damage-responsive cell fate regulator, which is negatively regulated by oncogenic signalling.[27,28,29,30,31,32] In undamaged cells HIPK2 is rapidly degraded by the ubiquitin ligase Siah-1.33–35 After DNA damage, HIPK2 is activated and stabilized through a concerted mechanism including autophosphorylation, recruitment of the phosphorylation-guided cis/trans isomerase Pin[1] and ATM-mediated Siah-1 phosphorylation.[33,36,37] Upon severe. We show that SIRT1 activity is restricted in response to severe DNA damage through phosphorylation of SIRT1 by HIPK2 at PML-NBs
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