Scaffold subunit of some HBO1 complexes, which have a histone H4 acetyltransferase activity (By similarity). 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 (PubMed:25018020). Positive regulator of neurogenesis (PubMed:25018020). 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 (By similarity). Interacts (via C-terminus) with KDM1A (via AOD/Tower domain) (PubMed:25018020). The first PHD domain is essential for its E3 ubiquitin ligase activity. Strongly decreased level of KDM1A polyubiquitination resulting in increased level of KDM1A protein. Decelerated emergence of neural progenitors and mature neurons. Embryonic stem cells grow in aggregates with smoother-edged, rounder-shaped cell clones and fail to organize in rosettes with surrounding cells exhibiting neuronal morphology with extensive arborization. Decreased expression of neural markers. Belongs to the JADE family. Extended N-terminus.