The impact of endoplasmic reticulum (ER) stress on the miR-122 promoter activity. (A) There are three hepatocyte nuclear factor 4 alpha (HNF4A) binding sites present in miR-122 promoter, which explain why HNF4A downregulation decreases miR-122 under stress. (B) The effect of small molecule inhibitors targeted to signal transducer and activator of transcription 3 (STAT3), Janus kinase 1 (JAK1), protein kinase RNA-like ER kinase (PERK) and ER stress on the miR-122 promoter regulation. Uninfected and hepatitis C virus (HCV)-infected Huh-7.5 cells were transfected with one microgram of miR-122 promoter-construct with firefly luciferase. Following the transfection step, cells were treated with or without thapsigargin (TG), sulforaphane, and STAT3 inhibitors. After 24 hours, the luciferase activity was measured. Luciferase assays were performed three times. (C) ER stress activator regulation of miR-122 promoter. (D) The impact of a nuclear factor erythroid 2-related factor 2 (NRF2) activator, sulforaphane, on miR-122 promoter activity. The results are expressed as the mean ± standard deviation (SD) of three experiments. Error bars represent SD. p-values were calculated by ANOVA between different groups as compared to untreated HCV-infected group. ** p-value < 0.01, *** p-value < 0.001.