E4F1 coordinates pyruvate metabolism and the activity of the elongator complex to ensure protein translation fidelity during neuronal development

The Leigh syndrome is a severe inborn neurodegenerative encephalopathy that is commonly associated with pyruvate metabolism defects. The transcription factor E4F1, a key regulator of the pyruvate dehydrogenase complex (PDC), was previously found to be mutated in Leigh syndrome patients but the molecular mechanisms leading to cell death in E4F1-deficient neurons remain unknown. Here, we show that E4F1 coordinates a transcriptional program involved in AcetylCoenzyme A (AcCoA) production by the PDC and its utilization by the Elongator complex to acetylate tRNAs and thereby enhance protein translation fidelity in the central nervous system. E4F1 directly regulates the expression of Dlat and Elp3, two genes encoding key subunits of the PDC and the Elongator complex. Consistently, genetic inactivation of E4f1 in neurons during mouse embryonic development decreased the activity of the PDC and of the Elongator complex, resulting in impaired tRNAs editing and the induction of an endoplasmic reticulum (ER) stress / unfolded protein response (UPR) that led to neuronal cell death and microcephaly. Impaired expression of ELP3 and activation of an ATF-driven UPR response was also observed in fibroblasts from Leigh syndrome patients harboring a homozygous E4F1K144Q mutation. Our findings identify a novel crosstalk between pyruvate metabolism and the regulation of protein translation that is perturbed in Leigh syndrome patients. mRNA profiles of 3 brains of E14.5 wild type (WT) and E4f1 KO (KO) mice.Leigh综合征（Leigh syndrome）是一类严重的先天性神经退行性脑病，通常与丙酮酸代谢缺陷相关。转录因子E4F1是丙酮酸脱氢酶复合物（pyruvate dehydrogenase complex, PDC）的关键调控因子，既往研究已在Leigh综合征患者中发现该因子存在突变，但E4F1缺陷神经元引发细胞死亡的分子机制至今仍未阐明。本研究证实，E4F1可协同调控一套转录程序，该程序既参与PDC介导的乙酰辅酶A（AcetylCoenzyme A, AcCoA）生成，又可调控延伸复合物（Elongator complex）利用AcCoA对转运RNA（tRNAs）进行乙酰化修饰，从而增强中枢神经系统内的蛋白质翻译保真度。E4F1可直接调控Dlat与Elp3的基因表达，这两个基因分别编码PDC与延伸复合物的关键亚基。与之相符的是，在小鼠胚胎发育阶段的神经元中特异性敲除E4f1基因，会降低PDC与延伸复合物的活性，导致tRNA修饰受损，并诱发内质网（endoplasmic reticulum, ER）应激/未折叠蛋白反应（unfolded protein response, UPR），最终引发神经元细胞死亡与小头畸形。携带纯合E4F1K144Q突变的Leigh综合征患者的成纤维细胞中，同样观察到ELP3表达受损以及ATF介导的未折叠蛋白反应激活。本研究揭示了丙酮酸代谢与蛋白质翻译调控之间的全新串扰通路，该通路在Leigh综合征患者中发生紊乱。本数据集包含3只E14.5野生型（wild type, WT）小鼠脑组织与3只E4f1基因敲除（knockout, KO）小鼠脑组织的mRNA表达谱。