BRD4-mediated histone H4K12 lactylation drives ovarian cancer progression by activating the Ube2v1-DDX3X ubiquitination axis

BACKGROUND: Aberrant histone lactylation is emerging as a pivotal player in tumorigenesis. However, its role in epithelial ovarian cancer (EOC) has not been fully elucidated to date. METHODS: Histone lactylation levels were detected using western blotting and immunohistochemistry in EOC and their prognostic value was evaluated. By integrating CUT&Tag and RNA-seq data, we pinpointed Ubiquitin-conjugating E2 enzyme variant 1(Ube2v1) as the crucial gene regulated by Histone H4K12 lactylation (H4K12la). The role of H4K12la on enhancing Ube2v1 expression was confirmed through RT-PCR, western blotting, ChIP, and dual-luciferase reporter assays. Target proteins interacting with and regulated by Ube2v1 were identified using IP-MS and validated by Co-IP. A histone modification compound library was used to screen potential modulators of H4K12la. MALDI-TOF/TOF MS was used to detect in vitro enzymatic products to investigate the potential lactylation activity of BRD4. RESULTS: H4K12la was significantly elevated in EOC tissues and associated with poor patient survival. We identified Ube2v1 as a key target gene activated by H4K12la. Ube2v1 promoted EOC cell proliferation and inhibited apoptosis by forming a complex with Ubc13 to catalyze the K63-linked ubiquitination and subsequent autophagic degradation of DDX3X. Through a targeted compound screen, we discovered that BET inhibitors, especially inhibitors that target BRD4 via the PROTAC approach, could significantly downregulate the level of H4K12la. Crucially, our findings suggest that BRD4 might play a direct role in modulating H4K12 lactylation. The expression levels of BRD4, H4K12la, and Ube2v1 were positively correlated in clinical EOC samples and ovarian cancer cell lines. CONCLUSION: Our study uncovers a previously unrecognized function of BRD4 in regulating histone lactylation and delineates the oncogenic BRD4/H4K12la/Ube2v1/DDX3X axis in EOC. These findings not only provide a profound mechanistic insight into EOC progression but also firmly establish the therapeutic rationale for targeting BRD4, via PROTAC inhibitors, in the treatment of EOC.