Activation of SIRT1 by an N-terminal Regulatory Domain
Date of Award
Doctor of Philosophy (PhD)
The NAD+-dependent protein deacetylase SIRT1 regulates transcriptional responses and enzymatic functions involving energy metabolism, responses to stress, and aging and is thus a candidate drug target for the treatment of metabolic, inflammatory, and neurodegenerative diseases. However, the mechanism(s) controlling the activity of SIRT1 itself is poorly understood. SIRT1 overexpression or activation by small molecules has been shown to ameliorate disease phenotypes in both animal and cellular models of disease, making SIRT1 a high priority drug target. SIRT1 deacetylates many protein substrates including p53, HNF1- α , PPAR-γ , FOXO, NFκB, and Ku 70. The mechanism for selecting protein substrates is enigmatic since there is no defined sequence motif surrounding the acetyl-lysine targeted for deacetylation, and a variety of peptide substrates are accommodated in vitro. My thesis project aimed to understand how SIRT1 achieves its biological specialization for specific protein targets and cellular activities; specifically, the role of SIRT1's unique N-terminal domain in selecting substrates and activating SIRT1 enzymatic activity.
We have shown that the recombinant N-terminal (NTERM) domain (SIRT1 residues 1-221) trans-activates deacetylation activity, revealing an unprecedented mechanism for the regulation of SIRT1 activity. The NTERM domain physically interacts with endogenous SIRT1 and promotes its association with protein substrates including the p65 subunit of NF-κB. Two motifs within the NTERM domain contribute to activation of SIRT1-dependent activities, and one of these motifs is targeted by the negative regulator, Deleted in Breast Cancer 1 (DBC1). These novel bipartite motifs interact with each other, and thus may function in cis to enhance substrate binding or allosterically control SIRT1 enzymatic activity. Our results provide a new rationale for the selective pharmacological control of SIRT1-dependent activities.
Chair and Committee
Tom E Ellenberger
Michael G Caparon, Daved Fremont, Shin-ichiro Imai, Helen Piwnica-Worms, Jason D Weber
Ghisays, Fiorella, "Activation of SIRT1 by an N-terminal Regulatory Domain" (2012). Arts & Sciences Electronic Theses and Dissertations. 85.