B, OTUB1 suppression decreases serum-induced ERK1/2 phosphorylation. Serum-starved A549 cells expressing shRNAs against OTUB1 or GFP were stimulated with 10% serum for the indicated time periods. Levels of phosphorylated ERK1/2 and total ERK1/2 were analyzed by Meso Scale assay. The results are expressed as a mean of pERK1/2 levels relative to total ERK1/2 ± s.e.m; p-values were determined by two-sided t-Test, n=2. 