Higgins Reneé, Gendron Joshua M, Rising Lisa, Mak Raymond, Webb Kristofor, Kaiser Stephen E, Zuzow Nathan, Riviere Paul, Yang Bing, Fenech Emma, Tang Xin, Lindsay Scott A, Christianson John C, Hampton Randolph Y, Wasserman Steven A, Bennett Eric J
Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
Cancer Structural Biology, Oncology Medicinal Chemistry, Pfizer Worldwide Research and Development, 10770 Science Center Drive, San Diego, CA 92121, USA.
Mol Cell. 2015 Jul 2;59(1):35-49. doi: 10.1016/j.molcel.2015.04.026. Epub 2015 Jun 4.
Insults to ER homeostasis activate the unfolded protein response (UPR), which elevates protein folding and degradation capacity and attenuates protein synthesis. While a role for ubiquitin in regulating the degradation of misfolded ER-resident proteins is well described, ubiquitin-dependent regulation of translational reprogramming during the UPR remains uncharacterized. Using global quantitative ubiquitin proteomics, we identify evolutionarily conserved, site-specific regulatory ubiquitylation of 40S ribosomal proteins. We demonstrate that these events occur on assembled cytoplasmic ribosomes and are stimulated by both UPR activation and translation inhibition. We further show that ER stress-stimulated regulatory 40S ribosomal ubiquitylation occurs on a timescale similar to eIF2α phosphorylation, is dependent upon PERK signaling, and is required for optimal cell survival during chronic UPR activation. In total, these results reveal regulatory 40S ribosomal ubiquitylation as an important facet of eukaryotic translational control.
内质网（ER）稳态受到破坏会激活未折叠蛋白反应（UPR），该反应会提高蛋白质折叠和降解能力，并减弱蛋白质合成。虽然泛素在调节错误折叠的内质网驻留蛋白降解中的作用已得到充分描述，但泛素依赖性调节UPR过程中的翻译重编程仍未得到充分研究。利用全球定量泛素蛋白质组学，我们鉴定出40S核糖体蛋白的进化保守、位点特异性调节泛素化。我们证明这些事件发生在组装好的细胞质核糖体上，并且受到UPR激活和翻译抑制的刺激。我们进一步表明，内质网应激刺激的调节性40S核糖体泛素化发生的时间尺度与真核起始因子2α（eIF2α）磷酸化相似，依赖于蛋白激酶R样内质网激酶（PERK）信号传导，并且在慢性UPR激活期间对最佳细胞存活是必需的。总之，这些结果揭示了调节性40S核糖体泛素化是真核生物翻译控制的一个重要方面。
