ASSAY DEVELOPMENT AND INHIBITION OF DEUBIQUITINASES

Deubiquitinases (DUBs) counteract ubiquitination by removing or trimming ubiquitin chains to alter the ubiquitin signal. Studying and targeting DUBs is of high importance due to their roles in cellular processes and involvements in several diseases such as in cancer. The recent developments of unique probes and reagents using chemical synthesis of proteins became very instrumental in supporting these efforts. Here, we will present a protein synthetic approach that enables the rapid synthesis of differently modified labeled-ubiquitinated peptides to facilitate rapid optimization of DUBs substrates.¹ Furthermore, it has been recently shown that some DUBs are regulated by reactive oxygen species (ROS) in which the catalytic Cys residue undergoes reversible oxidation, hence modulating DUBs activity under oxidative stress. In this regards, we will show how small molecules that are capable of generating ROS efficiently inhibit DUBs by selective and non-reversible oxidation of the catalytic Cys residue.² Interestingly, the small molecule beta-lapachone, which is currently in clinical trials for cancer, is among our list of the potent inhibitors suggesting possible new cellular targets for its therapeutic effects.

1. a) S. Ohayon, L. Spasser, A. Aharoni, A. Brik, J. Am. Chem. Soc. 2012, 134, 3281-3289. b) S. Ohayon, M. Refua, A. Brik , Org. Biomol. Chem. 2015, DOI: 10.1039/C5OB01142F.
2. S. Ohayon, M. Refua, A. Hendler, A. Aharoni, A. Brik, Angewandte Chemie Int. Ed. 2015, 54, 599-603.