RELA and nutritional disorder: Importantly, there was no apparent difference in the levels of S536-phosphorylated NF-κB p65 between DFO-treated and untreated cells in the presence of calyculin A, suggesting that iron deficiency inhibits PP1 and/or PP2A; the result of this is the promotion of S536 phosphorylation of NF-κB p65 (Figure 5E).