The tumor suppressor SirT2 regulates cell cycle progression and genome stability by modulating the mitotic deposition of H4K20 methylation

Abstract

The establishment of the epigenetic mark H4K20me1 (monomethylation of H4K20) by PR-Set7 during G 2 /M directly impacts S-phase progression and genome stability. However, the mechanisms involved in the regulation of this event are not well understood. Here we show that SirT2 regulates H4K20me1 deposition through the deacetylation of H4K16Ac (acetylation of H4K16) and determines the levels of H4K20me2/3 throughout the cell cycle. SirT2 binds and deacetylates PR-Set7 at K90, modulating its chromatin localization. Consistently, SirT2 depletion significantly reduces PR-Set7 chromatin levels, alters the size and number of PR-Set7 foci, and decreases the overall mitotic deposition of H4K20me1. Upon stress, the interaction between SirT2 and PR-Set7 increases along with the H4K20me1 levels, suggesting a novel mitotic checkpoint mechanism. SirT2 loss in mice induces significant defects associated with defective H4K20me1-3 levels. Accordingly, SirT2-deficient animals exhibit genomic instability and chromosomal aberrations and are prone to tumorigenesis. Our studies suggest that the dynamic cross-talk between the environment and the genome during mitosis determines the fate of the subsequent cell cycle.

SIRT 7 promotes genome integrity and modulates non‐homologous end joining DNA repair

“…Although the recruitment of 53BP1 to DNA damage sites is only partially impaired in the absence of SIRT7, this is not unusual in other models in which chromatin remodeling at DSB is compromised. Some examples include the Suv4‐20h histone methyltransferase double‐null mice, in which H4K20me2 is reduced (Schotta et al , 2008); the SIRT2 KO mice by its impact on the H4K20me1 methyl transferase PRSET7 (Serrano et al , 2013). …”

“…I‐SceI‐GR‐RFP was a gift from Tom Misteli (Addgene plasmid # 17654). H3K18 mutants, SIRT7‐Flag, and SIRT7‐H188Y‐Flag were subcloned into the pMSCVpuro vector and retroviral particles were generated as described previously (Serrano et al , 2013). …”

“…IF assays were carried out as previously described (Serrano et al , 2013). Images were acquired using a LSM510 META confocal microscope (Carl Zeiss).…”

“…Cell cycle and polyploidy analysis was performed as previously described (Serrano et al , 2013). For cell survival analysis, thymocytes were stained with Annexin V‐FITC (eBiosciences) and 7AAD (Pharmingen) using standard methods.…”

“…As this regulation fails, genome integrity can diminish, resulting in devastating consequences on cellular fitness, cumulatively leading to organismal aging. Indeed, numerous studies from yeast to mice support a role for sirtuins in the amelioration of human aging‐related pathologies (Guarente, 2013), and its deletion is associated with genome instability and compromised organismal viability (Cheng et al , 2003; McBurney et al , 2003; Mostoslavsky et al , 2006; Wang et al , 2008a; Serrano et al , 2013). …”