Figure 5.

Inhibition of RNA polymerase down-regulates baseline p53 mRNA and blocks PGE₂-promoted increases in p53 mRNA. B cells were activated with BCR:CD21-L, IL-4 and BAFF. After d 4 of culture, 1 set of replicate cultures received a pulse with 5 μM actinomycin D (42), while another set received vehicle alone. After a period of 15 min, a subset of each of the above were subsequently pulsed with PGE₂ (50 nM) or vehicle alone and cultured for an additional 8 h. Cultures were harvested, RNA was isolated, cDNA was prepared, and levels of p53 transcript were assessed by qPCR. Mean ± se fold Δ values are shown as in Fig. 2, for a total of 4 experiments.