Fig. 2

SJFα and SJFδ degradation of p38 isoforms is rapid, sustained, and proteasome dependent. a MDA-MB-231 cells were either pre-treated or not with the proteasome inhibitor epoxomicin (1 µM) or the neddylation inhibitor MLN4924 (1 µM) for 30 min and subsequently treated with either vehicle (DMSO), SJFα (250 nM), or SJFδ (250 nM) for 6 h. b Quantitative real-time PCR was performed after 24 h of treatment with either vehicle (DMSO), SJFα (250 nM), or SJFδ (250 nM) in MDA-MB-231 cells. The dotted line represents DMSO-treated conditions standardized to a value of 1.0 and mRNA abundance (per treatment group) is represented as a fold-change relative to that value. Data are based on biological duplicates and are normalized to beta-tubulin. Error bars denote s.d. c Cycloheximide (CHX) chase assay. MDA-MB-231 cells were pre-treated with 100 µg mL⁻¹ CHX for 1 h prior to treating for the indicated times with either vehicle (DMSO), SJFα (250 nM), or SJFδ (250 nM). Tubulin-normalized p38α and p38δ abundance values are reported beneath individual lanes. d MDA-MB-231 cells were treated with either vehicle (DMSO), SJFα (250 nM), or SJFδ (250 nM) for 24 h before re-plating onto new plastic in fresh medium for an additional 24, 48, or 72 h (“washout” conditions)