Scaffold subunit of some HBO1 complexes, which have a histone H4 acetyltransferase activity (PubMed:16387653). Acts as a E3 ubiquitin-protein ligase mediating the ubiquitination and subsequent proteasomal degradation of target protein histone demethylase KDM1A (PubMed:25018020). Also acts as a ubiquitin ligase E3 toward itself. Positive regulator of neurogenesis (By similarity). 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 the HBO1 complex composed at least of ING4 or ING5, MYST2/HBO1, MEAF6, and one of JADE1, JADE2 and JADE3 (PubMed:16387653). Interacts (via C-terminus) with KDM1A (via AOD/Tower domain) (PubMed:25018020). The first PHD domain is essential for its E3 ubiquitin ligase activity. Belongs to the JADE family. Extended N-terminus. Truncated N-terminus.