Professional Education


  • Doctor of Philosophy, Stanford University, GENE-PHD (2017)
  • Bachelor of Science, Massachusetts Institute of Technology, Biology (2009)

All Publications


  • Mono-unsaturated fatty acids link H3K4me3 modifiers to C. elegans lifespan NATURE Han, S., Schroeder, E. A., Silva-Garica, C. G., Hebestreit, K., Mair, W. B., Brunet, A. 2017; 544 (7649): 185-?

    Abstract

    Chromatin and metabolic states both influence lifespan, but how they interact in lifespan regulation is largely unknown. The COMPASS chromatin complex, which trimethylates lysine 4 on histone H3 (H3K4me3), regulates lifespan in Caenorhabditis elegans. However, the mechanism by which H3K4me3 modifiers affect longevity, and whether this mechanism involves metabolic changes, remain unclear. Here we show that a deficiency in H3K4me3 methyltransferase, which extends lifespan, promotes fat accumulation in worms with a specific enrichment of mono-unsaturated fatty acids (MUFAs). This fat metabolism switch in H3K4me3 methyltransferase-deficient worms is mediated at least in part by the downregulation of germline targets, including S6 kinase, and by the activation of an intestinal transcriptional network that upregulates delta-9 fatty acid desaturases. Notably, the accumulation of MUFAs is necessary for the lifespan extension of H3K4me3 methyltransferase-deficient worms, and dietary MUFAs are sufficient to extend lifespan. Given the conservation of lipid metabolism, dietary or endogenous MUFAs could extend lifespan and healthspan in other species, including mammals.

    View details for DOI 10.1038/nature21686

    View details for Web of Science ID 000398897900028

    View details for PubMedID 28379943

    View details for PubMedCentralID PMC5391274

  • p19(Arf) is required for the cellular response to chronic DNA damage. Oncogene Bieging-Rolett, K. T., Johnson, T. M., Brady, C. A., Beaudry, V. G., Pathak, N., Han, S., Attardi, L. D. 2016; 35 (33): 4414-4421

    Abstract

    The p53 tumor suppressor is a stress sensor, driving cell cycle arrest or apoptosis in response to DNA damage or oncogenic signals. p53 activation by oncogenic signals relies on the p19(Arf) tumor suppressor, while p53 activation downstream of acute DNA damage is reported to be p19(Arf)-independent. Accordingly, p19(Arf)-deficient mouse embryo fibroblasts (MEFs) arrest in response to acute DNA damage. However, p19(Arf) is required for replicative senescence, a condition associated with an activated DNA damage response, as p19(Arf)-/- MEFs do not senesce after serial passage. A possible explanation for these seemingly disparate roles for p19(Arf) is that acute and chronic DNA damage responses are mechanistically distinct. Replicative senescence may result from chronic, low-dose DNA damage responses in which p19(Arf) has a specific role. We therefore examined the role of p19(Arf) in cellular responses to chronic, low-dose DNA-damaging agent treatment by maintaining MEFs in low oxygen and administering 0.5 G y γ-irradiation daily or 150 μM hydroxyurea, a replication stress inducer. In contrast to their response to acute DNA damage, p19(Arf)-/- MEFs exposed to chronic DNA damage do not senesce, revealing a selective role for p19(Arf) in senescence upon low-level, chronic DNA damage. We show further that p53 pathway activation in p19(Arf)-/- MEFs exposed to chronic DNA damage is attenuated relative to wild-type MEFs, suggesting a role for p19(Arf) in fine-tuning p53 activity. However, combined Nutlin3a and chronic DNA-damaging agent treatment is insufficient to promote senescence in p19(Arf)-/- MEFs, suggesting that the role of p19(Arf) in the chronic DNA damage response may be partially p53-independent. These data suggest the importance of p19(Arf) for the cellular response to the low-level DNA damage incurred in culture or upon oncogene expression, providing new insight into how p19(Arf) serves as a tumor suppressor. Moreover, our study helps reconcile reports suggesting crucial roles for both p19(Arf) and DNA damage-signaling pathways in tumor suppression.

    View details for DOI 10.1038/onc.2015.490

    View details for PubMedID 26725325

    View details for PubMedCentralID PMC4931997

  • Cell biology. Lysosomal lipid lengthens life span. Science Han, S., Brunet, A. 2015; 347 (6217): 32-33

    View details for DOI 10.1126/science.aaa4565

    View details for PubMedID 25554778

  • Histone methylation makes its mark on longevity TRENDS IN CELL BIOLOGY Han, S., Brunet, A. 2012; 22 (1): 42-49

    Abstract

    How long organisms live is not entirely written in their genes. Recent findings reveal that epigenetic factors that regulate histone methylation, a type of chromatin modification, can affect lifespan. The reversible nature of chromatin modifications suggests that therapeutic targeting of chromatin regulators could be used to extend lifespan and healthspan. This review describes the epigenetic regulation of lifespan in diverse model organisms, focusing on the role and mode of action of chromatin regulators that affect two epigenetic marks, trimethylated lysine 4 of histone H3 (H3K4me3) and trimethylated lysine 27 of histone H3 (H3K27me3), in longevity.

    View details for DOI 10.1016/j.tcb.2011.11.001

    View details for Web of Science ID 000299450400005

    View details for PubMedID 22177962

    View details for PubMedCentralID PMC3253950

  • Members of the H3K4 trimethylation complex regulate lifespan in a germline-dependent manner in C. elegans NATURE Greer, E. L., Maures, T. J., Hauswirth, A. G., Green, E. M., Leeman, D. S., Maro, G. S., Han, S., Banko, M. R., Gozani, O., Brunet, A. 2010; 466 (7304): 383-U137

    Abstract

    The plasticity of ageing suggests that longevity may be controlled epigenetically by specific alterations in chromatin state. The link between chromatin and ageing has mostly focused on histone deacetylation by the Sir2 family, but less is known about the role of other histone modifications in longevity. Histone methylation has a crucial role in development and in maintaining stem cell pluripotency in mammals. Regulators of histone methylation have been associated with ageing in worms and flies, but characterization of their role and mechanism of action has been limited. Here we identify the ASH-2 trithorax complex, which trimethylates histone H3 at lysine 4 (H3K4), as a regulator of lifespan in Caenorhabditis elegans in a directed RNA interference (RNAi) screen in fertile worms. Deficiencies in members of the ASH-2 complex-ASH-2 itself, WDR-5 and the H3K4 methyltransferase SET-2-extend worm lifespan. Conversely, the H3K4 demethylase RBR-2 is required for normal lifespan, consistent with the idea that an excess of H3K4 trimethylation-a mark associated with active chromatin-is detrimental for longevity. Lifespan extension induced by ASH-2 complex deficiency requires the presence of an intact adult germline and the continuous production of mature eggs. ASH-2 and RBR-2 act in the germline, at least in part, to regulate lifespan and to control a set of genes involved in lifespan determination. These results indicate that the longevity of the soma is regulated by an H3K4 methyltransferase/demethylase complex acting in the C. elegans germline.

    View details for DOI 10.1038/nature09195

    View details for Web of Science ID 000279867100052

    View details for PubMedID 20555324

    View details for PubMedCentralID PMC3075006