Moores Cancer Center, University of California San Diego, La Jolla, CA, 92093, USA.
Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA, 92093, USA.
Blood Cancer J. 2020 Feb 6;10(2):16. doi: 10.1038/s41408-020-0282-9.
Large-scale chromosomal translocations are frequent oncogenic drivers in acute myeloid leukemia (AML). These translocations often occur in critical transcriptional/epigenetic regulators and contribute to malignant cell growth through alteration of normal gene expression. Despite this knowledge, the specific gene expression alterations that contribute to the development of leukemia remain incompletely understood. Here, through characterization of transcriptional regulation by the RUNX1-ETO fusion protein, we have identified Ras-association domain family member 2 (RASSF2) as a critical gene that is aberrantly transcriptionally repressed in t(8;21)-associated AML. Re-expression of RASSF2 specifically inhibits t(8;21) AML development in multiple models. Through biochemical and functional studies, we demonstrate RASSF2-mediated functions to be dependent on interaction with Hippo kinases, MST1 and MST2, but independent of canonical Hippo pathway signaling. Using proximity-based biotin labeling we define the RASSF2-proximal proteome in leukemia cells and reveal association with Rac GTPase-related proteins, including an interaction with the guanine nucleotide exchange factor, DOCK2. Importantly, RASSF2 knockdown impairs Rac GTPase activation, and RASSF2 expression is broadly correlated with Rac-mediated signal transduction in AML patients. Together, these data reveal a previously unappreciated mechanistic link between RASSF2, Hippo kinases, and Rac activity with potentially broad functional consequences in leukemia.
大规模染色体易位是急性髓细胞白血病（AML）中频繁的致癌驱动因素。这些易位通常发生在关键的转录/表观遗传调节剂中，并通过改变正常基因表达导致恶性细胞生长。尽管有了这些知识，但导致白血病发展的确切基因表达改变仍不完全清楚。在这里，通过 RUNX1-ETO 融合蛋白的转录调控特征分析，我们确定 Ras 相关结构域家族成员 2（RASSF2）是一种关键基因，在 t（8;21）相关 AML 中异常转录抑制。RASSF2 的重新表达特异性抑制多种模型中的 t（8;21）AML 发展。通过生化和功能研究，我们证明 RASSF2 介导的功能依赖于与 Hippo 激酶 MST1 和 MST2 的相互作用，但独立于经典 Hippo 途径信号。使用基于邻近的生物素标记，我们定义了白血病细胞中 RASSF2 近端蛋白质组，并揭示了与 Rac GTPase 相关蛋白的关联，包括与鸟嘌呤核苷酸交换因子 DOCK2 的相互作用。重要的是，RASSF2 敲低会损害 Rac GTPase 的激活，并且 RASSF2 的表达与 AML 患者中的 Rac 介导的信号转导广泛相关。总之，这些数据揭示了 RASSF2、Hippo 激酶和 Rac 活性之间以前未被认识的机制联系，在白血病中具有潜在的广泛功能后果。
