ATP-dependent RNA helicase. Required for mRNA export and translation regulation during spermatid development. ATP + H2O = ADP + H(+) + phosphate Detected in both cytoplasm and nucleus of testicular cells. Also detected in chromatoid bodies of round spermatids. Isoform 1 is expressed in germ cells. Isoform 2 is expressed in Leydig cells and in round spermatids of adult testis upon gonadotropin stimulation. Phosphorylated on threonine residues. The phosphorylated form is found in the cytoplasm but not in the nucleus. Male mice display normal sexual behavior but are sterile with testes that are 25% smaller than the wild-type. Round spermatids arrest at step 8 and fail to elongate. Chromatoid bodies are unusually condensed, greatly reduced in size and lack the typical amorphous texture throughout all steps of spermiogenesis. Belongs to the DEAD box helicase family.