The blood system serves as a key model for cell differentiation and cancer. It is orchestrated by precise spatiotemporal expression of the hematopoietic master regulator PU.1. PU.1 gene expression is regulated through enhancer-promoter interactions within a topologically associated domain (TAD). PU.1 levels increase during myeloid differentiation while failure to do so results in myeloid leukemia. In contrast, T-cell differentiation requires PU.1 to be completely switched off. Little is known about the precise mechanisms of PU.1 repression, physiological as in T-cell differentiation, or pathological as in leukemia. Here we demonstrate that the down-regulation of PU.1 mRNA is a dynamic process involving an alternative promoter in intron 3 that is induced by RUNX transcription factors driving noncoding antisense transcription. Core binding factor (CBF) fusions, RUNX1-ETO and CBFβ-MYH11 in t(8;21) and inv(16) acute myeloid leukemia (AML), activate the PU.1 antisense promoter, thus shifting from sense towards antisense transcription and blocking myeloid differentiation. In patients with CBF-AML, we found that an elevated antisense/sense ratio represents a hallmark compared to normal karyotype AML or healthy CD34+ cells. Competitive interaction of the enhancer with the proximal or the antisense promoter are at the heart of differential PU.1 expression during myeloid and T-cell development. Leukemic CBF fusions thus utilize a physiologic mechanism employed by T-cells to decrease sense PU.1 transcription. Our results identify the first example of a sense/antisense promoter competition as a crucial functional switch for gene expression perturbation by oncogenes. This novel basic disease mechanism reveals a previously unknown Achilles heel for future precise therapeutic targeting of oncogene-induced chromatin remodeling.

中文翻译：

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核心结合因子白血病劫持T细胞倾向性PU.1反义启动子

血液系统是细胞分化和癌症的关键模型。它是由造血主调节子PU.1的精确时空表达精心安排的。PU.1基因表达通过拓扑相关域（TAD）中的增强子-启动子相互作用来调控。在髓样分化过程中，PU.1水平升高，而未能做到这一点会导致髓样白血病。相反，T细胞分化要求PU.1完全关闭。对PU.1抑制的确切机制，如T细胞分化的生理学或白血病的病理学知之甚少。在这里，我们证明了PU.1 mRNA的下调是一个动态过程，涉及内含子3中的替代启动子，该启动子由RUNX转录因子驱动非编码反义转录而诱导。t（8; 21）和inv（16）急性髓细胞性白血病（AML）中的核心结合因子（CBF）融合体RUNX1-ETO和CBFβ-MYH11激活PU.1反义启动子，从而从有义向反义转录和阻止骨髓分化。在患有CBF-AML的患者中，我们发现与正常的核型AML或健康的CD34 +细胞相比，反义/反义比率的升高代表了标志。增强子与近端或反义启动子的竞争性相互作用是髓样和T细胞发育过程中差异PU.1表达的核心。因此，白血病CBF融合利用T细胞所采用的生理机制来减少有义PU.1转录。我们的结果确定了有义/反义启动子竞争的第一个例子，它是癌基因干扰基因表达的关键功能开关。