The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
Cambridge Institute of Therapeutic Immunology and Infectious Disease, Jeffrey Cheah Biomedical Centre, Cambridge Biomedical Campus, Cambridge, Cambridgeshire CB2 0AW, UK.
Mol Cell. 2023 Jun 1;83(11):1921-1935.e7. doi: 10.1016/j.molcel.2023.04.023. Epub 2023 May 17.
Although most eukaryotic proteins are targeted for proteasomal degradation by ubiquitination, a subset have been demonstrated to undergo ubiquitin-independent proteasomal degradation (UbInPD). However, little is known about the molecular mechanisms driving UbInPD and the degrons involved. Utilizing the GPS-peptidome approach, a systematic method for degron discovery, we found thousands of sequences that promote UbInPD; thus, UbInPD is more prevalent than currently appreciated. Furthermore, mutagenesis experiments revealed specific C-terminal degrons required for UbInPD. Stability profiling of a genome-wide collection of human open reading frames identified 69 full-length proteins subject to UbInPD. These included REC8 and CDCA4, proteins which control proliferation and survival, as well as mislocalized secretory proteins, suggesting that UbInPD performs both regulatory and protein quality control functions. In the context of full-length proteins, C termini also play a role in promoting UbInPD. Finally, we found that Ubiquilin family proteins mediate the proteasomal targeting of a subset of UbInPD substrates.
虽然大多数真核生物蛋白质通过泛素化被靶向到蛋白酶体降解，但已经证实有一部分蛋白质发生泛素非依赖性蛋白酶体降解（UbInPD）。然而，关于驱动 UbInPD 的分子机制以及涉及的降解基序，我们知之甚少。利用 GPS 肽组学方法（一种用于降解基序发现的系统方法），我们发现了数千个促进 UbInPD 的序列；因此，UbInPD 的普遍性比目前人们的认识要高。此外，突变实验揭示了 UbInPD 所需的特定 C 末端降解基序。对人类开放阅读框全基因组文库的稳定性分析确定了 69 个全长蛋白质受 UbInPD 调控。其中包括控制增殖和存活的 REC8 和 CDCA4 蛋白，以及错误定位的分泌蛋白，这表明 UbInPD 既具有调节功能，也具有蛋白质质量控制功能。在全长蛋白质的背景下，C 末端也在促进 UbInPD 方面发挥作用。最后，我们发现泛素结合酶家族蛋白介导了一部分 UbInPD 底物的蛋白酶体靶向。
