HBx down-regulates miR-520b through binding to Sp1 with partner survivin. (A) The expression levels of miRNA-520b, miRNA-520e, miRNA-29a and miRNA-181c were examined by qRT-PCR in LO2-X-S/LO2-X cells. (B) The expression of miR-520b in clinical HCC and peritumor samples was detected by qRT-PCR. (C) A model shows Sp1 binding site-directed mutation in the promoter region of miR-520b. (D) The effect of knockdown of Sp1 on miR-520b in LO2-X-S or HepG2.2.15 cells was examined by qRT-PCR analysis (***P < 0.001, Student’s t test). (E) The effect of Sp1 on miR-520b promoter in LO2-X-S cells was tested using Sp1 siRNA (Si-Sp1) or Sp1 mutant by luciferase reporter gene assays (**P < 0.01, Student’s t test). (F-H) The interaction among HBx, survivin and Sp1 in a complex was examined by co-IP. (I) Interaction of the complex, including HBx, survivin and Sp1, with the promoter region of miR-520b was examined by ChIP in LO2-X-S cells.