Probable RNA helicase. Required for RNA-mediated gene silencing by the RNA-induced silencing complex (RISC). Required for both miRNA-mediated translational repression and miRNA-mediated cleavage of complementary mRNAs by RISC (By similarity). 5' to 3' RNA helicase contributing to UPF1 mRNA target degradation by translocation along 3' UTRs. Required for microRNA (miRNA)-mediated gene silencing by the RNA-induced silencing complex (RISC). Required for both miRNA-mediated translational repression and miRNA-mediated cleavage of complementary mRNAs by RISC. In cooperation with FMR1, regulates miRNA-mediated translational repression by AGO2 (By similarity). May function as a messenger ribonucleoprotein (mRNP) clearance factor (By similarity). ATP + H2O = ADP + H(+) + phosphate Belongs to the DNA2/NAM7 helicase family. SDE3 subfamily.