Association of HuR-TAP fusion protein mimicking phosphorylated residue S100 with HuR target mRNAs. (A) HEK-293 cells were transfected with plasmids to express HuR-TAP fusion proteins (WT or bearing a phosphomimic mutation S100D). (B) HuR binding was assessed as explained in Figure 5. The enrichment of each mRNA in HuR(S100D)TAP IPs compared with HuR(WT)TAP IPs is indicated. The average of 2 similar experiments is shown.