Figure 4 : IC50 analyses of four inhibitors for selected DUBs.

From: Screening of DUB activity and specificity by MALDI-TOF mass spectrometry

Figure 4

A subset of four inhibitors was chosen to characterize in more detail by determining their IC50 for three DUBs. BAY 11-7082, NSC 697923 and SJB3-019A were chosen as they have some selectivity for one DUB, HBX 41,108 was chosen as it has been proposed as a USP7 inhibitor which is an attractive drug target51. Small inhibitor compounds were pre-incubated for 35 min at different concentrations (0–30 or 0–100 μM) in triplicates (that is, three different experiments) and subsequently the specific substrate was added and incubated for 60 min (30 °C). Diubiquitin topoisomers used for each DUB are named on the y axis. Data show that NSC 697923 and BAY 11-7082 inhibit strongly USP7 with IC50<0.2 μM, while HBX 41,108 inhibits it at ~6 μM. SJB3-019A inhibits USP8 and USP2 about 10-fold better than USP1. See also Supplementary Table 4 for P values. Error bars represent s.d. of measurements. For statistical analysis, four parameter logistic curve (best‐fit solution, nonlinear regression-dynamic fitting) and normality tests (Kolmogorov–Smirnov) are used (SigmaPlot, v. 12.5).