The potency of miRNA-mediated repression correlates with expression levels. (A) miRNA-Seq results from 1 μg of HeLa total RNA. Red dots indicate miRNAs of interest with their rank by cloning frequency shown in parentheses. (B) Scatter plot of the top 250 miRNAs from two HeLa miRNA-Seq experiments; miRNAs of interest are in red. (C) Schematic of the luciferase targeting constructs for miR-21, miR-130 and miR-502. The red sequences are the tandem target sites located in the 3′ UTR of the luciferase mRNA, and the black sequences are the miRNAs. (D) Ratios of firefly to renilla luciferase activities in HeLa cultures transfected with miRNA-reporter constructs. Shown is a representative result from three independent experiments. Error bars are the standard deviation from a single experiment where transfections were done in quadruplicate for each construct. (E) Schematic depicting the workflow for the optimized miRNA-Seq approach to profiling miRNAs.