Institute of Reproductive and Developmental Biology, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, Hammersmith Campus, London, United Kingdom.
Stem Cells. 2014 Aug;32(8):2111-22. doi: 10.1002/stem.1725.
Telomere repeat binding factor 2 (TRF2) is a component of the shelterin complex that is known to bind and protect telomeric DNA, yet the detection of TRF2 in extra-telomeric regions of chromosomes suggests other roles for TRF2 besides telomere protection. Here, we demonstrate that TRF2 plays a critical role in antagonizing the repressive function of neuron-restrictive silencer factor, also known as repressor element-1 silencing transcription factor (REST), during the neural differentiation of human embryonic stem cells (hESCs) by enhancing the expression of a truncated REST splice isoform we term human REST4 (hREST4) due to its similarity to rodent REST4. We show that TRF2 is specifically upregulated during hESC neural differentiation concordantly with an increase in the expression of hREST4 and that both proteins are highly expressed in NPCs. Overexpression of TRF2 in hESCs increases hREST4 levels and induces their neural differentiation, whereas TRF2 knockdown in hESCs and NPCs reduces hREST4 expression, hindering their ability to differentiate to the neural lineage. Concurrently, we show that TRF2 directly interacts with the C-terminal of hREST4 through its TRF2 core binding motif [F/Y]xL, protecting hREST4 from ubiquitin-mediated proteasomal degradation and consequently furthering neural induction. Thus, the TRF2-mediated counterbalance between hREST4 and REST is vital for both the generation and maintenance of NPCs, suggesting an important role for TRF2 in both neurogenesis and function of the central nervous system.
端粒重复结合因子 2（TRF2）是遮蔽体复合物的一个组成部分，已知它可以结合并保护端粒 DNA，但 TRF2 在染色体的端粒外区域的检测表明 TRF2 除了保护端粒之外还有其他作用。在这里，我们证明 TRF2 在拮抗神经元限制沉默因子（也称为沉默元件 1 沉默转录因子（REST））的抑制功能方面发挥着关键作用，该因子在人胚胎干细胞（hESC）的神经分化过程中，通过增强我们称之为人类 REST4（hREST4）的截断 REST 剪接异构体的表达来发挥作用，由于其与啮齿动物 REST4 的相似性，因此将其命名为 hREST4。我们表明，TRF2 在 hESC 神经分化过程中特异性上调，与 hREST4 的表达增加一致，并且这两种蛋白质在 NPC 中高度表达。在 hESCs 中过表达 TRF2 会增加 hREST4 水平并诱导其神经分化，而在 hESCs 和 NPCs 中敲低 TRF2 会降低 hREST4 的表达，从而阻碍其向神经谱系分化的能力。同时，我们表明 TRF2 通过其 TRF2 核心结合基序 [F/Y]xL 与 hREST4 的 C 端直接相互作用，保护 hREST4 免受泛素介导的蛋白酶体降解，从而进一步促进神经诱导。因此，TRF2 介导的 hREST4 和 REST 之间的平衡对于 NPC 的产生和维持至关重要，这表明 TRF2 在神经发生和中枢神经系统功能中都起着重要作用。
