Guo, R., Abdelmohsen, K., Morin, P.J., and Gorospe, M.
Notes: The let-7 microRNA family are thought to act as tumor suppressors. Let-7 activity is downregulated in several cancers, and overexpression of let-7 inhibits cancer growth in some mouse models. The authors of this paper describe a sensitive luciferase-based reporter assay for detecting let-7 miRNA activity in cells. The reporter construct was based on the pmirGLO Vector, which contains firefly luciferase as the reporter gene and Renilla luciferase as an internal control. The authors inserted let-7 miRNA target sites at the 3′ end of the firefly luciferase gene. Interaction of let-7 miRNA with these target sequences resulted in reduced luciferase activity. The authors used the reporter construct to screen a kinase inhibitor library for compounds that repress let-7 activity in ovarian cancer cells, and identified GSK-3β as a potential target for therapeutics. (4406)