EDC3 Phosphorylation Regulates Tumor Growth and Invasion Through Controlling Modifications in P-body Formation and Dynamics.

Regulation of mRNA stability and translation plays a critical role in determining protein abundance within cells. Processing bodies are critical regulators of these processes. We report that the Pim1 protein kinase binds to the internally disordered region of a core P-body component EDC3, enhancer of mRNA-decapping protein 3, inducing the phosphorylation of EDC3 on serine 161 which significantly modifies P-body activity and content. This phosphorylation is highly elevated in a large number of tumor cell types and prevents the localization of EDC3 to P-bodies. RNAs isolated from purified P-bodies using a unique methodology contain approximately seven thousand differentially distributed mRNAs compared to whole-cells. Treatment with protein kinase inhibitors alters approximately 4 percent of the translatable mRNAs elevating specific 5 prime sequences within P-bodies. Genome edited cells harboring the S161 to alanine mutation mimic a dephosphorylated state and block tumor cell migration and invasion, and dramatically suppress tumor growth in tissue culture and mouse xenograft models. These results demonstrate that EDC3 phosphorylation regulates multiple biological functions and the modulation of the specific mRNA content of P-bodies.

mRNA稳定性与翻译过程的调控，是决定细胞内蛋白质丰度的关键环节。加工小体（Processing bodies, P-bodies）是上述过程的核心调控因子。本研究发现，Pim1蛋白激酶可结合核心P-body组分EDC3（mRNA脱帽蛋白3增强子，enhancer of mRNA-decapping protein 3）的内部无序区域，诱导EDC3在丝氨酸161（serine 161）位点发生磷酸化，该修饰可显著改变P-body的活性与组分构成。该磷酸化事件在多种肿瘤细胞类型中显著上调，并会阻碍EDC3向P-body的定位。采用独特分离方法从纯化P-body中获取的RNA，与全细胞总RNA相比，约有7000种mRNA的分布存在显著差异。蛋白激酶抑制剂处理可改变约4%的可翻译mRNA，使P-body内的特定5'端序列丰度升高。携带S161A（丝氨酸161突变为丙氨酸）突变的基因组编辑细胞，可模拟EDC3的去磷酸化状态，能够阻断肿瘤细胞的迁移与侵袭，并在细胞培养及小鼠异种移植模型中显著抑制肿瘤生长。上述研究结果表明，EDC3的磷酸化可调控多项生物学功能，并能重塑P-body内特异性mRNA的组分组成。