UBE2M is a stress-inducible dual E2 for neddylation and ubiquitylation that promotes targeted degradation of UBE2F. Weihua Zhou et al.

UBE2M and UBE2F are two family members of neddylation E2 conjugating enzyme that, together with E3s, activate CRLs (Cullin-RING Ligases) by catalyzing cullin neddylation. However, whether and how two E2s cross-talk with each other are largely unknown. Here, we report that UBE2M is a stress-inducible gene subjected to cis-transactivation by HIF-1α and AP1, and MLN4924, a small molecule inhibitor of E1 NEDD8-activating enzyme (NAE), up-regulates UBE2M via blocking degradation of HIF-1α and AP1. UBE2M is a dual E2 for targeted ubiquitylation and degradation of UBE2F, acting as a neddylation E2 to activate CUL3-Keap1 E3 under physiological condition, but as an ubiquitylation E2 for Parkin-DJ-1 E3 under stressed conditions. UBE2M-induced UBE2F degradation leads to CRL5 inactivation and subsequent NOXA accumulation to suppress the growth of lung cancer cells. Collectively, our study establishes a negative regulatory axis between two neddylation E2s with UBE2M ubiquitylating UBE2F, and two CRLs with CRL3 inactivating CRL5.

UBE2M与UBE2F是类泛素化（neddylation）E2结合酶家族的两个成员，可与E3酶协同，通过催化Cullin蛋白的类泛素化修饰激活CRL（Cullin-RING连接酶，Cullin-RING Ligases, CRLs）。然而，这两种E2酶是否存在交叉对话以及具体的调控机制，目前仍知之甚少。本研究发现，UBE2M属于应激诱导型基因，可被HIF-1α（缺氧诱导因子-1α）与AP1（激活蛋白1）介导顺式反式激活；同时，作为NEDD8激活酶E1（NAE）的小分子抑制剂MLN4924，可通过阻断HIF-1α与AP1的降解而上调UBE2M的表达。UBE2M是同时介导UBE2F靶向泛素化（ubiquitylation）与降解的双重功能E2酶：在生理状态下，它作为类泛素化E2酶激活CUL3-Keap1 E3连接酶；而在应激条件下，则作为泛素化E2酶参与Parkin-DJ-1 E3连接酶的调控过程。UBE2M介导的UBE2F降解可导致CRL5失活，进而引发NOXA（促凋亡蛋白）积累，最终抑制肺癌细胞的增殖。综上，本研究构建了两类类泛素化E2酶之间的负调控轴：UBE2M通过泛素化修饰UBE2F，同时明确了CRL3与CRL5之间的负调控通路，即CRL3可使CRL5失活。