sentence: Nevertheless , to validate the predicted competition between miR-124 and pre-miR-124 to target SNAI2 3 ′ UTR , a reporter construct containing SNAI23 ′ UTR was co-transfected with either the mature form of miR-124 ( from a PolIII construct , sh-124 ) or the precursor form of miR-124 ( from a PolII construct , pEZX-124 ) .