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. Restricts retrotransposition of long interspersed element-1 (LINE-1) in cooperation with TUT4 and TUT7 counteracting the RNA chaperonne activity of L1RE1. Facilitates LINE-1 uridylation by TUT4 and TUT7 (By similarity). Required for embryonic viability and for normal central nervous system development and function. Plays two critical roles in early brain development: suppresses retroelements in the nucleus by directly inhibiting cDNA synthesis, while regulates cytoskeletal mRNAs to influence neurite outgrowth in the cytosol (By similarity). May function as a messenger ribonucleoprotein (mRNP) clearance factor (By similarity). ATP + H2O = ADP + H(+) + phosphate Interacts with DICER1, AGO2, TARBP2, EIF6 and RPL7A (60S ribosome subunit); they form a large RNA-induced silencing complex (RISC). Interacts with APOBEC3G in an RNA-dependent manner. Interacts with TRIM71 (via NHL repeats) in an RNA-dependent manner. Interacts with both protein products of LIRE1, ORF1p and ORF2p. Interacts with TUT4 and, to a lesser extent, TUT7; the interactions are RNA-dependent. Interacts with AGO2, TNRC6B and UPF1; the interactions are direct and RNA-dependent. Interacts with FMR1; this interaction is direct, occurs in an RNA-dependent manner on polysomes and induces association of MOV10 with RNAs. Interacts with SHFL; the interaction increases in presence of RNA (By similarity). Interacts with DHX34; the interaction is-RNA independent (By similarity). Co-enriched in cytoplasmic foci with TUT4 (By similarity). In developing neurons, localizes both in nucleus and cytoplasm, but in the adulthood it is only cytoplasmic (By similarity). Belongs to the DNA2/NAM7 helicase family. SDE3 subfamily.