ATP-dependent RNA helicase required during spermatogenesis to repress transposable elements and prevent their mobilization, which is essential for germline integrity. Acts via the piRNA metabolic process, which mediates the repression of transposable elements during meiosis by forming complexes composed of piRNAs and Piwi proteins and governs the methylation and subsequent repression of transposons. Involved in the primary piRNA metabolic process. Specifically binds to piRNA precursors and promotes the generation of intermediate piRNA processing fragments that are subsequently loaded to Piwi proteins. Acts via its ATP-dependent RNA helicase activity: displays 5'-3' RNA unwinding activity and probably mediates unwinding and funneling of single-stranded piRNA precursor transcripts to the endonuclease that catalyzes the first cleavage step of piRNA processing to generate piRNA intermediate fragments that are subsequently loaded to Piwi proteins. ATP + H2O = ADP + H(+) + phosphate Interacts with PIWIL1. Interacts with PIWIL2. Interacts with PIWIL4. Interacts with HSPA2. Interacts with PLD6. Component of the meiotic nuage, also named P granule, a germ-cell-specific organelle required to repress transposon activity during meiosis. Additional isoforms seem to exist. Specifically expressed in testis. Belongs to the DNA2/NAM7 helicase family. SDE3 subfamily.