Inhibition of human recombinant SAE1/2 assessed as inhibition of SUMO1-UbcH9 complex formation at 0.001 to 10 uM after 1.5 hrs by Western blot analysis
Biochemical Assay: Through the Molecular Library Probe Production Center Network (MLPCN), at least 300,000 compounds were screened using a TR-FRET method, an ALPHASCREEN method or both, and tested for their ability to inhibit SUMOylation of a target protein via SUMO E1 or SUMO E2. The assays were based on SUMOylation of the target protein RanGAP1, which is a protein that is efficiently SUMOylated with only the SUMO E1 and E2 enzymes, and does not use E3 ligases. A fluorescence resonance energy transfer (FRET) assay was the primary assay followed by a chemoluminescence-based secondary assay using ALPHA screen to eliminate false positive hits. Then, the hits were screened by a poly-ubiquitination assay using ubiquitin, ubiquitin E1, Ubc5 and Apc11 to eliminate inhibitors not specific to SUMOylation. The screening identified a potent family of SUMOylation inhibitors based on a tricyclic scaffold.
Inhibition of SAE (unknown origin) assessed as decrease in SAE-mediated Ubc9-SUMO conjugation levels up to 10 uM preincubated for 10 mins followed by ATP and Mg2+ addition measured after 60 mins by Western blot analysis
Inhibition of SAE-mediated Ubc9-SUMO conjugation in human Caco2 cells up to 10 uM preincubated for 10 mins followed by ATP and Mg2+ addition measured after 60 mins by Western blot analysis
Inhibition of recombinant SAE (unknown origin) assessed as reduction in transfer of SUMO1 to UBC9 using SUMO1 as a substrate in presence of ATP at Km concentration by HTRF assay
Inhibition of SAE in human HCT116 cells assessed as reduction in redistribution of SUMO2/3 proteins from nucleus to cytosol incubated for 4 hrs by immunofluorescence assay