FIG. 3.

Effects of ATRA pretreatment on PKCβ expression and responsiveness to TPA-induced SAPK activation. (A) HL-60 and HL-525 cells were cultured in the presence or absence of 1 μM ATRA for 3 days. Lysates from the indicated cells were subjected to immunoblot analysis with anti-PKCβII, anti-PKCα, and anti-PKCδ antibodies. (B) HL-525 cells were pretreated with ATRA for 3 days and then exposed to 16 nM TPA for the indicated times. Anti-SAPK antibody immunoprecipitates were assayed for GST-Jun phosphorylation.