Scaffold subunit of some HBO1 complexes, which have a histone H4 acetyltransferase activity. Plays a key role in HBO1 complex by directing KAT7/HBO1 specificity towards histone H4 acetylation (H4K5ac, H4K8ac and H4K12ac), regulating DNA replication initiation, regulating DNA replication initiation. Component of the HBO1 complex composed. Localizes to the ciliary transition zone. The 2 PHD-type zinc fingers are required for transcriptional activity. Belongs to the JADE family.