Association of HuR's point mutated at Chk2 phosphorylation sites with target mRNAs. (A) Schematic of point-mutated HuR residues phosphorylated by Chk2 (top) and HuR-TAP proteins expression in transfected HEK-293 cells. Cells were left untreated, treated with ATM or Chk2 inhibitors (10μM, 8 hours), or pretreated with ATM or Chk2 inhibitors for 2 hours, and then irradiated (1 Gy, 6 hours). (B) Binding of HuR-TAP chimeric proteins HuR target mRNAs was measured by TAP IP followed by quantitative RT-PCR. The individual enrichment of each mRNA in HuR-TAP fusion proteins IPs compared with TAP (vector control) IPs is indicated. The average of 2 similar experiments is shown.