Human PUS7 in tRNA pseudouridylation. Human PUS7 in tRNA pseudouridylation

Pseudouridine is the first discovered and the most frequent modification in RNA. However, its biological functions in physiology and human diseases are largely unknown. Here, we show that pseudouridine synthase PUS7 is differentially expressed in glioblastoma patient tissues verse non-tumor brain tissues, and highly expressed in patient brain-derived cancer stem cells, compared to normal brain-derived neural stem cells. Upregulated expression of PUS7 predicts worse survival in glioblastoma patients in multiple databases. Indeed, we show that PUS7 plays an important role in regulating the self-renewal and tumorigenesis of glioblastoma stem cells. Overexpression of the wild type but not the catalytically inactive PUS7 increases the growth and self-renewal of GSCs. In contrast, knockdown of PUS7 dramatically suppresses GSC growth, self-renewal and tumorigenesis. Mechanistically, knockdown of PUS7 activates interferon pathway through translational control of TYK2 via PUS7-regulated tRNAs. Moreover, we have identified chemical inhibitors for PUS7 in this study. These chemical compounds target pseudouridine modification and suppress GSC growth and tumorigenesis, providing a potential therapeutic tool for GBM treatment. Overall design: mRNA, rRNA, and small RNA Ψ-seq to detect PUS7 dependent pesudouridne sites in PBT003 cells, NSC006 and G13 treatment cells

假尿苷（pseudouridine）是首个被发现且在RNA中最常见的修饰形式，但其在生理过程及人类疾病中的生物学功能仍未得到充分阐明。本研究发现，假尿苷合酶PUS7（pseudouridine synthase PUS7）在胶质母细胞瘤患者组织与非肿瘤脑组织中存在差异表达；相较于正常脑源性神经干细胞，患者来源的脑肿瘤干细胞中PUS7的表达水平显著升高。PUS7表达上调可在多个公共数据库中预示胶质母细胞瘤患者的不良预后。研究证实，PUS7在调控胶质母细胞瘤干细胞（glioblastoma stem cells, GSCs）的自我更新与致瘤性方面发挥关键作用。过表达野生型PUS7而非催化失活型PUS7，可促进GSCs的增殖与自我更新；与之相反，敲低PUS7则可显著抑制GSCs的增殖、自我更新及致瘤能力。机制层面，敲低PUS7可通过靶向调控TYK2的翻译过程，借助PUS7所调控的转运RNA（transfer RNA, tRNAs）激活干扰素通路。此外，本研究还鉴定出PUS7的化学抑制剂，这类化合物可靶向假尿苷修饰过程，抑制GSCs的增殖与致瘤性，为胶质母细胞瘤（glioblastoma, GBM）的治疗提供了潜在的治疗策略。整体实验设计：对PBT003细胞、NSC006细胞以及经G13处理的细胞进行mRNA、rRNA及小RNA的Ψ-seq测序，以检测PUS7依赖性假尿苷修饰位点。