The present invention is a method for identifying agents which modulate microRNA activity. The invention involves contacting a cell harboring a microRNA and a microRNA binding sequence, which is operably linked to a nucleic acid molecule encoding a reporter protein, with a test agent increases or decreases the expression of the reporter protein thereby identifying a microRNA modulator. Antagonists identified by this screening assay are provided, as are methods for using the same to inhibit microRNA activity and prevent or treat disease.
