Regulation Of NF-κB Signaling Pathway By UFM1 Modification

Ubiquitin and ubiquitin-like protein(UBL)can regulate protein stability,location as well as interaction with other proteins through the posttranslational modification.UFM1(the ubiquitin-fold modifierl)is the newly identified ubiquitin-like protein,it almost exists in all eukaryotes,except fungi.Similar as Ubiquitin modification,UFM1 modification(Ufmylation)is accomplished through three-step enzymatic reaction:Firstly,the UFM1-activating enzyme 5(UBA5)serves as the E1 to activate UFM1.Then,Activated UFM1 is transferred to the active site of UFM1-conjugating enzyme 1’(UFC1,E2).Finally,ubiquitin-like ligase UFL1 acts as the E3 to transferred UFM1 to its substrate from E2.UFM1 has two specific proteases,UfSP1 and UfSP2,respectively.These two enzymes are involved in the processing of precursor UFM1 for the formation the mature UFM1.In addition,they also participated in the release of UFM1 from its substrate.The NF-κB signaling pathway is widespread in the cell signaling pathways,it regulates physiological and pathological process together with multiple cellular pathways.Nuclear factor kB(NF-κB)is a nuclear transcription factor that regulates the expression of varieties of downstream target genes.The NF-κB pathway comprises the canonical and the non-canonical pathway.Generally,under the stimulus,IKK protein complex is activated through receptors and joint-protein phosphorylate IκB protein,resulting in ubiquitinazation and degradation of IκB protein,and led to release the NF-κB dimers.NF-κB dimer is transferred to the nucleus for the regulation of target gene expression.Recent studies have discovered that DDRGK1 is one of substrates and a regulatory factor of UFM1.In addition,DDRGK1 can regulate the NF-κB signaling pathway.Therefore we speculate UFM1 can regulate NF-κB signaling pathway.In this report,we found that UFM1 increased the transcriptional activity of NF-κB.UFM1 silencing with UFM1 RNA interference inhibited the expression of downstream target genes at mRNA and protein levels.Our data showed that UFM1 can interact with IKKβand confirmed the IKKβ was a novel substrate of Ufmylation.In addition,we found that the level of Ser536 phosphorylation of p65 was decreased in UFM1 silencing cells.Consistently,we found that overexpression UFM1 promoted the nuclear localization of GFP-p65.Therefore,our results suggest that UFM1 may play a pivotal role in regulating NF-κB signaling pathway.