A methyltransferase-independent role for METTL1 in tRNA aminoacylation and oncogenic transformation

This submission is raw imaging data for our manuscript describing the following: Amplification of chromosomal material derived from 12q13-15 is common in human cancer, and believed to result in overexpression of multiple collaborating oncogenes. To define oncogenes involved, we overexpressed genes recurrently amplified in human liposarcoma using a zebrafish model of the disease. We found several genes whose overexpression collaborated with AKT in sarcomagenesis, including the tRNA methyltransferase METTL1. This was surprising because AKT phosphorylates METTL1 to inactivate its enzymatic activity. Indeed, phosphomimetic S27D or catalytically dead alleles phenocopied the oncogenic activity of wild-type METTL1. We found that METTL1 binds the multi-tRNA synthetase complex, which contains many of the cellular aminoacyl-tRNA synthetases, and promotes tRNA aminoacylation, polysome formation and protein synthesis independent of its methyltransferase activity. METTL1-amplified liposarcomas were hypersensitive to actinomycin D, a clinical inhibitor of ribosome biogenesis. Thus, METTL1 stimulates tRNA aminoacylation and protein synthesis independent of its methyltransferase activity, and this tumor-promoting function confers susceptibility to inhibition of ribosome biogenesis.本提交材料为对应研究论文的原始成像数据，该论文阐述如下内容：12号染色体q13-15区段来源的染色体物质扩增在人类癌症中颇为常见，且被认为会引发多个协同致癌基因的过表达。为明确其中涉及的致癌基因，我们利用该疾病的斑马鱼模型，对人类脂肪肉瘤中反复扩增的基因进行过表达操作。我们发现多个基因的过表达可在肉瘤发生过程中与AKT产生协同作用，其中包括tRNA甲基转移酶（tRNA methyltransferase）METTL1。这一结果颇为出人意料，因为AKT可通过磷酸化METTL1抑制其酶促活性。确实，磷酸模拟型S27D突变体或催化失活型等位基因均可模拟野生型METTL1的致癌活性。我们发现，METTL1能够结合多tRNA合成酶复合物——该复合物包含多种细胞内氨酰-tRNA合成酶——且可在不依赖自身甲基转移酶活性的前提下，促进tRNA氨酰化、多聚核糖体形成以及蛋白质合成。METTL1扩增型脂肪肉瘤对放线菌素D（actinomycin D）——一种临床常用的核糖体生物发生抑制剂——呈现高敏感性。综上，METTL1可通过不依赖自身甲基转移酶活性的途径促进tRNA氨酰化与蛋白质合成，而这一促肿瘤功能使得肿瘤对核糖体生物发生抑制剂具有易感性。