State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Protein Sciences, Frontiers Science Center for Cell Responses, National Demonstration Center for Experimental Biology Education and College of Life Sciences, Nankai University, Tianjin, China.
State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Tianjin, China.
Cell Death Differ. 2024 Nov;31(11):1534-1544. doi: 10.1038/s41418-024-01354-x. Epub 2024 Aug 6.
Erk signaling is indispensable for the self-renewal and differentiation of mouse embryonic stem cells (ESCs), as well as telomere homeostasis. But how Erk regulates these biological processes remains unclear. We identified 132 Erk2 interacting proteins by co-immunoprecipitation and mass spectrometric analysis, and focused on Ddx39 as a potential Erk2 substrate. We demonstrated that Erk2 phosphorylates Ddx39 on Y132 and Y138. Ddx39 knockout (KO) ESCs are defective in differentiation, due to reduced H3K27ac level upon differentiation. Phosphorylation of Ddx39 promotes the recruitment of Hat1 to acetylate H3K27 and activate differentiation genes. In addition, Ddx39 KO leads to telomere elongation in ESCs. Ddx39 is recruited to telomeres by the telomere-binding protein Trf1, consequently disrupting the DNA loop formed by Trf1 and suppressing the alternative lengthening of telomeres (ALT). Phosphorylation of Ddx39 weakens its interaction with Trf1, releasing it from telomeres. Thus, ALT activity is enhanced, and telomeres are elongated. Altogether, our studies reveal an essential role of Ddx39 in the differentiation and telomere homeostasis of ESCs.
Erk 信号对于小鼠胚胎干细胞（ESCs）的自我更新和分化以及端粒稳态是必不可少的。但是，Erk 如何调节这些生物过程尚不清楚。我们通过共免疫沉淀和质谱分析鉴定了 132 种 Erk2 相互作用蛋白，并将 Ddx39 作为潜在的 Erk2 底物进行了重点研究。我们证明 Erk2 在 Y132 和 Y138 位点使 Ddx39 磷酸化。Ddx39 敲除（KO）的 ESCs 在分化过程中出现缺陷，因为分化时 H3K27ac 水平降低。Ddx39 的磷酸化促进了 Hat1 的募集，从而乙酰化 H3K27 并激活分化基因。此外，Ddx39 KO 导致 ESCs 端粒延长。Ddx39 被端粒结合蛋白 Trf1 招募到端粒，从而破坏了由 Trf1 形成的 DNA 环，并抑制端粒的替代性延长（ALT）。Ddx39 的磷酸化削弱了它与 Trf1 的相互作用，使其从端粒中释放出来。因此，ALT 活性增强，端粒延长。总之，我们的研究揭示了 Ddx39 在 ESCs 的分化和端粒稳态中的重要作用。
