E3 ubiquitin ligase which catalyzes the covalent attachment of ubiquitin moieties onto substrate proteins (By similarity). Promotes the larval to adult transition by binding to the long non-coding RNA lep-5 to target the heterochronic protein lin-28 for degradation by the proteasome (PubMed:26811380, PubMed:30956008). This association and degradation of lin-28 also controls the timing of the sexual differentiation of individual neurons in males including the AIM, AWA, ADF, ASJ and CEM neurons (PubMed:31264582). Plays a role in governing the developmental timing of male tail tip morphogenesis (PubMed:26811380). Plays a role in two aspects of male mating behavior: response to hermaphrodite contact and vulva location (PubMed:26811380, PubMed:31264582). May play a role in the detection of preferred food sources (PubMed:31264582). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Component of a complex at least containing lep-2, lin-28 and the long non-coding RNA lep-5, which mediates the degradation of lin-28. Expressed in seam, tail tip, and other hypodermal cells, head and tail neurons, the pharynx, intestine and the developing hermaphrodite somatic gonad (PubMed:26811380, PubMed:31264582). Not expressed in body wall muscle cells (PubMed:26811380). Expressed from embryogenesis to adulthood (PubMed:26811380). Expressed in head neurons in L3 and L4 larvae (PubMed:31264582).