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. Together with fem-2 associates with the CBC(fem-1) E3 ubiquitin-protein ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of tra-1. Component of a complex containing fem-1, fem-2 and fem-3 (PubMed:23760267). Interacts with fem-1 and fem-2 (via N-terminus) (PubMed:23760267, PubMed:17609115). 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 (PubMed:17609115). Interacts with tra-1 (PubMed:17609115). Interacts with sel-10 (PubMed:15306688). Interacts with tra-2 (PubMed:10364161, PubMed:12477393). Expressed both maternally and zygotically.