State Key Laboratory of Medical Genomics and Shanghai Institute of Hematology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China;
Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China; and.
Blood. 2016 Jan 14;127(2):233-42. doi: 10.1182/blood-2015-03-626671. Epub 2015 Nov 6.
The AML1/ETO fusion protein is essential to the development of t(8;21) acute myeloid leukemia (AML) and is well recognized for its dominant-negative effect on the coexisting wild-type protein AML1. However, the genome-wide interplay between AML1/ETO and wild-type AML1 remains elusive in the leukemogenesis of t(8;21) AML. Through chromatin immunoprecipitation sequencing and computational analysis, followed by a series of experimental validations, we report here that wild-type AML1 is able to orchestrate the expression of AML1/ETO targets regardless of being activated or repressed; this is achieved via forming a complex with AML1/ETO and via recruiting the cofactor AP-1 on chromatin. On chromatin occupancy, AML1/ETO and wild-type AML1 largely overlap and preferentially bind to adjacent and distinct short and long AML1 motifs on the colocalized regions, respectively. On physical interaction, AML1/ETO can form a complex with wild-type AML1 on chromatin, and the runt homology domain of both proteins are responsible for their interactions. More importantly, the relative binding signals of AML1 and AML1/ETO on chromatin determine which genes are repressed or activated by AML1/ETO. Further analysis of coregulators indicates that AML1/ETO transactivates gene expression through recruiting AP-1 to the AML1/ETO-AML1 complex. These findings enrich our knowledge of understanding the significance of the interplay between the wild-type protein and the oncogenic fusion protein in the development of leukemia.
AML1/ETO 融合蛋白对于 t(8;21) 急性髓系白血病 (AML) 的发生发展至关重要，其对共存的野生型蛋白 AML1 的显性负效应已得到充分认识。然而，在 t(8;21) AML 的白血病发生过程中，AML1/ETO 与野生型 AML1 之间的全基因组相互作用仍难以捉摸。通过染色质免疫沉淀测序和计算分析，以及一系列的实验验证，我们在这里报告称，野生型 AML1 能够协调 AML1/ETO 靶基因的表达，而不论其被激活还是抑制；这是通过与 AML1/ETO 形成复合物以及在染色质上募集共因子 AP-1 来实现的。在染色质占据方面，AML1/ETO 和野生型 AML1 大部分重叠，并分别优先结合在共定位区域相邻且不同的短和长 AML1 基序上。在物理相互作用方面，AML1/ETO 可以在染色质上与野生型 AML1 形成复合物，并且这两种蛋白质的 runt 同源结构域负责它们的相互作用。更重要的是，染色质上 AML1 和 AML1/ETO 的相对结合信号决定了哪些基因被 AML1/ETO 抑制或激活。对共调节因子的进一步分析表明，AML1/ETO 通过将 AP-1 募集到 AML1/ETO-AML1 复合物上来反式激活基因表达。这些发现丰富了我们对理解野生型蛋白和致癌融合蛋白在白血病发生发展中的相互作用意义的认识。
