Fluorogenic Substrates and Cyclic Peptide Inhibitors of the Oligonucleotide Activated SIRT7

The sirtuins are NAD+-dependent lysine deacylases, comprising seven isoforms (SIRT1–7) in humans, which are involved in the regulation of a plethora of biology, including gene expression and metabolism. The sirtuins share a common hydrolytic mechanism but display preferences for different ε -N -acyllysine substrates. SIRT7 deacetylates targets in nuclei and nucleoli but remains one of the lesser studied of the seven isoforms; in part, because of a lack of chemical tools to specifically probe SIRT7 activity. Here we expressed SIRT7 and, using small-angle X-ray scattering, reveal SIRT7 to be a monomeric enzyme with low degree of globular flexibility in solution. We developed a fluorogenic assay for investigation of the substrate preferences of SIRT7 and to evaluate compounds that modulate its activity. We report several mechanism-based SIRT7 inhibitors and de novo cyclic peptide inhibitors selected from mRNA-display library screening; compounds that represent starting points for development of the needed SIRT7-specific chemical tools. ![Figure][1] TOC text Broad screening of the substrate specificity of SIRT7 revealed a strong preference for the cleavage of long chain acyl lysine modifications as well as amino acid sequence preferences. Further, the activity was substantially increased in the presence of oligonucleotides or nucleosome particles. Finally, mRNA display selection delivered a cyclopeptide with potency in the low micromolar range. ### Competing Interest Statement The authors have declared no competing interest. [1]: pending:yes