E3 ubiquitin ligase catalyzing the covalent attachment of ubiquitin moieties onto substrate proteins. 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. Expressed in testis, brain, heart and kidney. Ubiquitously detected at low levels throughout the entire embryo, but expression is highest in the ventricular layers of the brain. Expressed at the blastocyst stage and the embryonic days 8-17, as well as in undifferentiated and differentiated embryonic stem cells. Expressed in the arcuate nucleus of both male and female animals. Levels of expression are highest on postnatal days 10 and 12, begin to decline on day 15, and reaches a nadir by days 18 to 22, at which time expression is 10 to 20% of the levels detected at 10 days. The timing of the decline in protein expression correlated with the ages at which arcuate KISS1 and TAC2 have been shown to increase, heralding the onset of puberty. Imprinted, expressed from the paternal chromosome only. The maternal methylation is established promptly after fertilization prior to syngamy.