NUSAP1 Recruits DAXX to Suppress HIF‐Driven Triple‐Negative Breast Cancer Progression

Abstract Nucleolar and spindle‐associated protein 1 (NUSAP1) is critical for cancer progression. However, its function in cancers is context‐dependent, and emerging evidence indicates that NUSAP1 possesses tumor suppressor functions, although the underlying mechanisms remain uncharted. In this study, NUSAP1 depletion is found to significantly increases the proliferation, migration, and invasion of triple‐negative breast cancer (TNBC) cells in vitro and promotes TNBC progression in vivo, suggesting that NUSAP1 is a tumor suppressor in TNBC. Mechanistically, NUSAP1 bridges HIFα and the transcriptional repressor death domain‐associated protein (DAXX) through its microtubule‐associated domain (MAD) to recruit the methyltransferase SETDB1, thereby attenuating HIF transcriptional activity and the expression of its target genes by depositing the H3K9me3 repressive mark on hypoxia response elements (HREs). Intriguingly, an engineered MAD of NUSAP1, designated as Tumor Suppressor‐MAD (TS‐MAD), is developed, which effectively abrogates HIF transcriptional activity by bridging the DAXX‐HIF interaction, consequently inhibiting HIF‐driven TNBC progression. Moreover, NUSAP1 is identified as a novel HIF‐repressed gene in TNBC cells, and its expression level shows a negative correlation with clinical outcomes in TNBC patients. These findings establish an HIF‐NUSAP1 double‐negative feedback loop in TNBC and validate TS‐MAD as a potential therapeutic strategy for HIF‐driven cancer.