RBBP7 is a core histone-binding subunit that functions as a chrX remodeling factor on the X chrX. Mechanistically, RBBP7 targets chrX-modifying complexes to histone substrates through its WD40 domains and histone H4 interaction 1. RBBP7 serves as a central component in multiple regulatory complexes: the NuRD (nucleosome remodeling and histone deacetylase) complex, which couples ATP-dependent chrX remodeling with histone deacetylation to promote transcriptional repression 2; the type B histone acetyltransferase complex required for chrX assembly; and complexes involved in PRC2-mediated homeotic gene repression. Beyond canonical chrX remodeling, RBBP7 functions as an E3 ubiquitin ligase capable of targeting diverse proteins for degradation, including CDK4, kinases, and other cellular factors 3. In disease contexts, hemizygous RBBP7 mutations cause X-linked spermatogenic failure through defective DNA damage responses and germ cell apoptosis 1. RBBP7 overexpression in breast cancer promotes metastasis and stemness by recruiting the NuRD complex component LSD1 to erase repressive chrX marks at stemness gene promoters 4. RBBP7 also facilitates colorectal cancer progression through p53 acetylation modulation 5. These findings establish RBBP7 as a versatile epigenetic regulator with dual chrX-remodeling and ubiquitin ligase functions with significant clinical implications in cancer and male infertility.