Figure 2.

Human StAR mRNA contains a functional let-7 binding site at its 3′-UTR. (A) Bioinformatics predicted 1 binding site for let-7b at position1467 in the 3′UTR of human StAR. Partial sequences of StAR (in red) and sequence of let-7b (in green) are shown. Base-paired interactions between the microRNA seed region and the target mRNA are indicated by dots. Numbers are in nucleotides relative to the transcriptional start site of StAR. (B) psiCHECK2-StAR, the let-7 reporter construct, containing a 60-nt long fragment from human StAR at the 3′-UTR of a Renilla luciferase gene, along with a downstream constitutively expressed firefly luciferase (FFL) gene and a polyA (pA) signal to reduce background. psiCHECK2-let7-4x, which harbors 4 copies of let7 binding sites in the 3′-UTR of the Renilla luciferase gene, was used as a positive control. (C) Indicated reporter constructs were individually transfected into HEK293 cells, together with control miRNA (Ctr), let-7b, or miR-16, at a final concentration of 12 or 24 nM. Luciferase activities were measured 18 h post-transfection. Results are representative of three independent transfection experiments. Numbers are mean ± SD (n = 3). **P < 0.01.