Jiangsu Key Laboratory of Neuropsychiatric Diseases and College of Pharmaceutical Sciences, Jiangsu Province Engineering Research Center of Precision Diagnostics and Therapeutics Development, Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, Suzhou Key Laboratory of Drug Research for Prevention and Treatment of Hyperlipidemic Diseases, Soochow University, Suzhou, Jiangsu, China.
Department of Pathology, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China.
J Biol Chem. 2024 Oct;300(10):107751. doi: 10.1016/j.jbc.2024.107751. Epub 2024 Sep 10.
It has been revealed recently that the RNA-binding motif protein RBM39 is highly expressed in several cancers, which results in poor patient survival. However, how RBM39 is regulated in gastric cancer cells is unknown. Here, affinity purification-mass spectrometry and a biochemical screening are employed to identify the RBM39-interacting proteins and the deubiquitinating enzymes that regulate the RBM39 protein level. Integration of the data obtained from these two approaches uncovers USP39 as the potential deubiquitinating enzyme that regulates RBM39 stability. Bioinformatic analysis discloses that USP39 is increased in gastric cancer tissues and its elevation shortens the duration of overall survival for gastric cancer patients. Biochemical experiments verify that USP39 and RBM39 interact with each other and highly colocalize in the nucleus. Expression of USP39 elevates while USP39 knockdown attenuates the RBM39 protein level and their interaction regulates this modulation and their colocalization. Mechanistic studies reveal that USP39 reduces the K48-linked polyubiquitin chains on RBM39, thus enhancing its stability and increasing the protein level by preventing its proteasomal degradation. USP39 overexpression promotes while its knockdown attenuates the growth, colony formation, migration, and invasion of gastric cancer cells. Interestingly, overexpression of RBM39 partially restores the impact of USP39 depletion, while RBM39 knockdown partially abolishes the effect of USP39 overexpression on the growth, colony formation, migration, and invasion of gastric cancer cells. Collectively, this work identifies the first DUB for RBM39 and elucidates the regulatory functions and the underlying mechanism, providing a possible alternative approach to suppressing RBM39 by inhibiting USP39 in cancer therapy.
最近有研究表明，RNA 结合基序蛋白 RBM39 在多种癌症中高表达，导致患者生存预后较差。然而，RBM39 在胃癌细胞中的调控机制尚不清楚。本研究采用亲和纯化-质谱分析和生化筛选鉴定了 RBM39 的相互作用蛋白和调节 RBM39 蛋白水平的去泛素化酶。整合这两种方法获得的数据揭示了 USP39 是潜在的去泛素化酶，可调节 RBM39 的稳定性。生物信息学分析显示，USP39 在胃癌组织中表达增加，其水平升高会缩短胃癌患者的总生存期。生化实验证实 USP39 和 RBM39 相互作用，并高度共定位于细胞核内。USP39 的表达增加，而 USP39 敲低则降低 RBM39 蛋白水平，其相互作用调节这种调节及其共定位。机制研究表明，USP39 减少了 RBM39 上的 K48 连接的多泛素链，从而通过阻止其蛋白酶体降解来增强其稳定性并增加其蛋白水平。USP39 过表达促进，而敲低则抑制胃癌细胞的生长、集落形成、迁移和侵袭。有趣的是，RBM39 的过表达部分恢复了 USP39 耗竭的影响，而 RBM39 的敲低部分消除了 USP39 过表达对胃癌细胞生长、集落形成、迁移和侵袭的影响。综上所述，本研究鉴定了 RBM39 的第一个去泛素化酶，并阐明了其调节功能和潜在机制，为通过抑制 USP39 抑制 RBM39 在癌症治疗中的作用提供了一种可能的替代方法。
