Abstract
Protein homeostasis is tightly controlled by the coordinated actions of E3 ubiquitin ligases and deubiquitinases (DUBs). We previously identified Spindlin-4 (SPIN4), a histone H3K4me3 reader, as a degradation substrate of DCAF16. In this study, we confirmed this degradation pathway using an E3 ligase-focused CRISPR-Cas9 knockout screen. Furthermore, through a DUB-focused CRISPR-Cas9 knockout screen and biochemical analyses, we demonstrated that the deubiquitinase BAP1 interacts with and stabilizes SPIN4 via its deubiquitination activity. Inhibition or loss of BAP1 reduces SPIN4 levels, highlighting its critical role in maintaining SPIN4 homeostasis. Proteomics and interactome analyses further support this regulatory axis. These findings reveal a dynamic balance controlling SPIN4 stability, with potential implications for epigenetic regulation and disease processes.