Hasumi Mayuka, Ito Hayato, Machida Kodai, Niwa Tatsuya, Taminato Tomoya, Nagai Yoshitaka, Imataka Hiroaki, Taguchi Hideki
School of Life Science and Technology, Institute of Science Tokyo, Yokohama, Japan.
Department of Applied Chemistry, Graduate School of Engineering, University of Hyogo, Himeji, Hyogo, Japan.
J Biol Chem. 2025 Apr;301(4):108360. doi: 10.1016/j.jbc.2025.108360. Epub 2025 Feb 25.
The repeat expansion in the human genome contributes to neurodegenerative disorders such as spinocerebellar ataxia (SCA) and amyotrophic lateral sclerosis. Transcripts with repeat expansions undergo noncanonical translation called repeat-associated non-AUG (RAN) translation. The NOP56 gene, implicated in SCA36, contains a GGCCTG repeat in its first intron. In tissues of patients with SCA36, poly (Gly-Pro) and poly (Pro-Arg) peptides, likely produced through NOP56 RAN translation in (NOP56-RAN), have been detected. However, the detailed mechanism underlying NOP56-RAN remains unclear. To address this, we used cell-free translation systems to investigate the mechanism of NOP56-RAN and identified the following features. (i) Translation occurs in all reading frames of the sense strand of NOP56 intron 1. (ii) Translation is initiated in a 5' cap-dependent manner from near-cognate start codons upstream of the GGCCUG repeat in each frame. (iii) Longer GGCCUG repeats enhance NOP56-RAN. (iv) A frameshift occurs within the GGCCUG repeat. These findings provide insights into the similarities between NOP56-RAN and other types of RAN translation.
人类基因组中的重复序列扩增与神经退行性疾病相关，如脊髓小脑共济失调（SCA）和肌萎缩侧索硬化症。具有重复序列扩增的转录本会经历一种非经典翻译，即重复序列相关的非AUG（RAN）翻译。与SCA36相关的NOP56基因在其第一个内含子中含有一个GGCCTG重复序列。在SCA36患者的组织中，已检测到可能通过NOP56的RAN翻译（NOP56-RAN）产生的聚（甘氨酸-脯氨酸）和聚（脯氨酸-精氨酸）肽。然而，NOP56-RAN的详细机制仍不清楚。为了解决这个问题，我们使用无细胞翻译系统来研究NOP56-RAN的机制，并确定了以下特征。（i）翻译发生在NOP56内含子1有义链的所有阅读框中。（ii）翻译以5'帽依赖的方式从每个阅读框中GGCCUG重复序列上游的近同源起始密码子开始。（iii）更长的GGCCUG重复序列会增强NOP56-RAN。（iv）在GGCCUG重复序列内会发生移码。这些发现为深入了解NOP56-RAN与其他类型RAN翻译之间的相似性提供了线索。
