BANF1 is downregulated by IRF1-regulated microRNA-203 in cervical cancer.

MicroRNAs (miRNAs) play important roles in various biological processes and are closely associated with the development of cancer. In fact, aberrant expression of miRNAs has been implicated in numerous cancers. In cervical cancer, miR-203 levels are decreased, although the cause of this aberrant expression remains unclear. In this study, we investigate the molecular mechanisms regulating miR-203 gene transcription. We identify the miR-203 transcription start site by 5' rapid amplification of cDNA ends and subsequently identify the miR-203 promoter region. Promoter analysis revealed that IRF1, a transcription factor, regulates miR-203 transcription by binding to the miR-203 promoter. We also demonstrate that miR-203 targets the 3' untranslated region of BANF1, thus downregulating its expression, whereas miR-203 expression is driven by IRF1. MiR-203 is involved in cell cycle regulation and overexpression of miR-203 suppresses cervical cancer cell proliferation, colony formation, migration and invasion. The inhibitory effect of miR-203 on the cancer cells is partially mediated by downregulating its target, BANF1, since knockdown of BANF1 also suppresses colony formation, migration and invasion.