Fig. 4. Effect of the overexpression of the RBP-J mutant on the prostanoid biosynthesis pathway. Cells were transfected with RBP-J DN (a mutated form of RBP-J) or empty (mock) plasmids and treated for 6, 24 or 48 hours with IL-1 (10 ng/ml) or vehicle (control). (A) PLA₂-IIA transcripts were assayed by RT-PCR. Results are expressed as a percentage of the PLA₂-IIA mRNA level of control cells and represent the mean ± s.e.m. of three independent experiments. (B) Secretion of PLA₂ and PGE₂ was expressed as a percentage of that of control cells. The basal PLA₂ secretion from mock-transfected cells was 3.6±0.9 and 4.1±0.6 pmol/min/µg RNA, 24 and 48 hours after transfection, respectively. For RBP-J DN-transfected cells, this parameter was 4.9±0.7 and 4.5±0.8 pmol/min/µg RNA. The basal PGE₂ secretion levels from mock and RBP-J-DN-transfected cells were 16.9±1.5 and 18.3±0.9 pg/ml, respectively. The data represent the mean ± s.e.m. of four to five independent experiments. RBP-J DN versus mock: *, P<0.05; **, P<0.01.