DNA damage-induced miR-23a regulates TOP1 expression. A shows that overexpression of miR-23a attenuates the cytoxicity of TOP1 poison irinotecan. Wild-type and miR-23a overexpressed HCC cells were treated with irinotecan and cell viability was determined by MTT assay. B shows that miR-23a was up-regulated upon DNA damage. Cells were exposed to UV-C for 10 min followed by 24 h culture. Total RNA was collected and miR-23a was detected by RT-qPCR. C shows miR-23a was transcriptionally activated upon DNA damage; RNA was collected and the pri-miR-23a and pre-miR-23a were detected as described.