HDACIs mediate phosphorylation of ATF-2 and CREB1. Western blot analysis was performed with mouse monoclonal phosphorylated ATF-2 (p-ATF-2) and rabbit polyclonal p-CREB1 antibodies and protein isolated from K562 cells. Total nonphosphorylated CREB (t-CREB) and t-ATF-2 levels were analyzed as loading controls (see “Material and methods”). (A) A representative blot for ATF-2 phosphorylation by drug treatments is shown. (B) A representative blot for drug-mediated CREB1 phosphorylation is shown. (C) The quantitative data for p-ATF-2 (Thr 71) and p-CREB1 (Ser 133) levels after NaB (2 mM), TSA (0.5 μM), or 100 ng/mL anisomycin (ANI) treatment alone (□) or after pretreatment with 10 μM SB203580 (▪) are shown. Data are presented as the fold increase in phosphorylated protein ± SEM. The star above the graph represents a comparison between untreated () and treated cells; the bracket and star represent a comparison between the different treatment conditions as indicated. Significance was achieved at the P < .05 level.