Figure 4. circKIF4A acts as a sponge of miR-1231 in papillary thyroid cancer. (A) 18S, GAPDH, circKIF4A and KIF4A in nuclear and cytoplasmic part analyzed by RT-qPCR. (B) Predicted interaction site of miR-1231 within the circKIF4A sequence. (C) miR-1231 expression in papillary thyroid cancer cell lines. (D) Luciferase reporter assay of TPC-1 and KAT-5 cells transfected with miR-1231 mimics and circKIF4A. (E) MS2-based RIP assay transfected with MS2bs-circKIF4A, MS2bs-circKIF4A-mt or Rluc control. (F) GSH/GSSG ratio was detected. GSH/GSSG ratio was increased after overexpression of miR-1231 which could be reversed by silencing circKIF4A.