Despite absent expression in normal hematopoiesis, the Forkhead factor FOXC1, a critical mesenchymal differentiation regulator, is highly expressed in ∼30% of HOXA^high acute myeloid leukemia (AML) cases to confer blocked monocyte/macrophage differentiation. Through integrated proteomics and bioinformatics, we find that FOXC1 and RUNX1 interact through Forkhead and Runt domains, respectively, and co-occupy primed and active enhancers distributed close to differentiation genes. FOXC1 stabilizes association of RUNX1, HDAC1, and Groucho repressor TLE3 to limit enhancer activity: FOXC1 knockdown induces loss of repressor proteins, gain of CEBPA binding, enhancer acetylation, and upregulation of nearby genes, including KLF2. Furthermore, it triggers genome-wide redistribution of RUNX1, TLE3, and HDAC1 from enhancers to promoters, leading to repression of self-renewal genes, including MYC and MYB. Our studies highlight RUNX1 and CEBPA transcription factor swapping as a feature of leukemia cell differentiation and reveal that FOXC1 prevents this by stabilizing enhancer binding of a RUNX1/HDAC1/TLE3 transcription repressor complex to oncogenic effect.

尽管叉头因子 FOXC1 在正常造血过程中不表达，但它是一种关键的间充质分化调节因子，在约 30% 的 HOXA^高急性髓系白血病 (AML) 病例中高表达，导致单核细胞/巨噬细胞分化受阻。通过整合蛋白质组学和生物信息学，我们发现 FOXC1 和 RUNX1 分别通过 Forkhead 和 Runt 结构域相互作用，并共同占据分布在分化基因附近的启动子和活性增强子。 FOXC1 稳定 RUNX1、HDAC1 和 Groucho 阻遏蛋白 TLE3 的关联，以限制增强子活性： FOXC1敲低会诱导阻遏蛋白的丢失、CEBPA 结合的增加、增强子乙酰化以及附近基因（包括KLF2）的上调。此外，它还触发 RUNX1、TLE3 和 HDAC1 从增强子到启动子的全基因组重新分配，导致自我更新基因（包括MYC和MYB）的抑制。我们的研究强调 RUNX1 和 CEBPA 转录因子交换是白血病细胞分化的一个特征，并揭示 FOXC1 通过稳定 RUNX1/HDAC1/TLE3 转录抑制复合物的增强子结合来防止这种情况发生，从而产生致癌作用。