Direct interaction between let-7a and 3'UTR of CCR7. (a) Preparation of the construct with the let-7a binding site on the 3'UTR of CCR7, which was predicted by the TargetScan 4.1 database program. (b) Luciferase activity of CCR7 3'UTR luciferase reporters was detected after synthetic let-7a transfection. Wild-type (WT) and mutant type (MUT) of CCR7 3'UTR luciferase reporters were prepared as described in the Material and Methods section. Expression of β-galactosidase was used as a control for transfection normalization.