Required for male development. In XO (male) animals, fem-3 directs male differentiation in all tissues. In XX (hermaphrodite animals), it specifies the first 80 or so germ cells to be sperm. Negatively regulates male development when bound to tra-2. Component of a complex containing fem-1, fem-2 and fem-3 (By similarity). Interacts with fem-1 and fem-2 (via N-terminus) (By similarity). Part of a E3 ubiquitin-protein ligase complex, at least composed of cul-2, elc-1, tra-1, fem-1, fem-2 and fem-3; mediates the ubiquitination and subsequent proteasomal degradation of tra-1 (By similarity). Interacts with sel-10 (By similarity). Interacts with tra-2 (PubMed:12477393).