Hepatitis C virus represses the cellular antiviral response by upregulating the expression of signal transducer and activator of transcription 3 through sponging microRNA‑122.

microRNAs (miRNAs) are small, non-coding RNAs that inhibit the expression of target protein coding genes at the post-transcriptional level. miR-122 is a liver specific miRNA. Notably, miR-122 is used by the hepatitis C virus (HCV) for triggering viral replication by interacting with the 5' untranslated region of the HCV RNA. The present study demonstrated that miR-122 inhibited the expression of signal transducer and activator of transcription 3 (STAT3), an antivirus response repressor. The HCV RNA acted as an 'miRNA sponge', which upregulated the expression of STAT3 by sealing miR-122. Subsequently, it was confirmed that this miR-122 sponge function of HCV RNA repressed the expression of polyinosinic-polycytidylic acid-stimulated type I interferons. The present study provided a deeper understanding of the complex role of miR-122 in the progression of HCV infection and supported the miR-122 inhibition strategy in anti-HCV infection treatment.