Catalyzes the synthesis of dihydrouridine, a modified base, in various RNAs, such as tRNAs, mRNAs and some long non-coding RNAs (lncRNAs) . Mainly modifies the uridine in position 47 (U47) in the D-loop of most cytoplasmic tRNAs . Also able to mediate the formation of dihydrouridine in some mRNAs, thereby regulating their translation .