ZNF512B associates with mitotic spindles, regulates metaphase exit and is crucial for stem cell differentiation

Zinc finger proteins are a large family of DNA-binding factors that play key roles in diverse cellular processes including gene regulation, RNA metabolism and cell cycle control. The zinc finger protein ZNF512B has recently been implicated in chromatin organization and transcriptional repression through its direct interaction with the nucleosome remodeling and deacetylase (NuRD) complex, its DNA-binding ability, and its association with the histone variant H2A.Z. Here, we uncover a previously unrecognized role for ZNF512B that is independent of both its zinc finger domains and NuRD association. We identify ZNF512B as a spindle-associated factor that regulates progression through mitosis, specifically controlling metaphase exit. ZNF512Bs N-terminal internal region, which contains 25 repeats of a six-residue motif predicted to form a {beta}-helix structure, is required and sufficient for its spindle interaction. Elevated ZNF512B levels result in a profound metaphase arrest that is ultimately lethal, a phenotype arising from the combined activity of its spindle-binding and chromatin-tethering functions. Conversely, ZNF512B depletion accelerates stem cell proliferation, impairs differentiation, and upregulates genes linked to cell cycle progression. Our findings position ZNF512B as a multifunctional protein that acts as a transcriptional repressor, a chromatin aggregator and a novel metaphase exit regulator through spindle fiber binding.