| JMJD8 is a member of Jumonji C domain-containing histone demethylase,which can demethylate multiple histone or non-histone lysine sites and participate in various biological processes in cells.Previous studies have shown that JMJD8 is located in the lumen of endoplasmic reticulum and can involve in angiogenesis by regulating cellular metabolism through binding to PKM2.Although JMJD8 plays a key role in cell process through different biological pathways,its corresponding molecular mechanism remain to be elucidated.This study focused on the effects of JMJD8 on AKT-related signal pathway and revealed for the first time that JMJD8,as a negative regulator,participates in tumor cell proliferation,DNA damage repair and tumor metastasis.Part Ⅰ:JMJD8 regulates tumor proliferation and repair of radiation damage.The most important chromatin damage caused by radiation is the DNA double-strand breaks(DSBs).In this research,we found that knockdown of JMJD8 in cancer cells significantly increased cell proliferation,and attenuated ionizing irradiation or etoposide treatment-induced DNA double-strand breaks level through enhancing the expression of Ku70 and Ku80 which are key participants in the non-homologous end-joining repair of DSBs.Moreover,attenuated JMJD8 expression enhanced the activation of AKT/NF-κB/COX-2 signaling pathway,which thereby upregulated the expression of Ku70 and Ku80.The results from the present research provided evidence to show the potential role of JMJD8 in repair of DSBs which induced by ionizing irradiation or chemo-therapy drug.We indicated that JMJD8 is a potential target for enhancing the efficacy of tumor radio-and chemo-therapies.Part Ⅱ:JMJD8 affects the invasion and migration of tumor cells.Epithelial-Mesenchymal transformation(EMT)can induce tumor cell invasion and metastasis,which is one of the hallmark events of tumor malignancy.In this research,we demonstrated that knockdown of JMJD8 stimulated phosphorylation of AKT and downstream GSK3β,followed by increased phosphorylation of β-catenin Ser552/Ser675 and decreased phosphorylation of β-catenin Thr33/37/Ser41 which enhanced accumulation and nucleus translocation of β-catenin.The upregulation of β-catenin can activate the expression of downstream target MMP9 and c-Myc,which promote EMT,and eventually lead to tumor cell invasion and migration.Our work found the molecular mechanism that attenuated JMJD8 expression induced EMT process through AKT/GSK3β/β-catenin signaling pathway,and analyzed the new pathway of JMJD8 affecting tumor invasion and migration,which proposed a new idea and potential bioactive markers for tumor treatment.Part Ⅲ:JMJD8 regulates post-translational modification of AKT.Methylation modification by histone methylase not only occurs on histone,but also non-histone proteins.In this research,we indicated that JMJD8 has a critical role in regulating membrane translocation and kinase activity of AKT through SETDB1-mediated AKT methylation.JMJD8-knockdown induced SETDB1-mediated AKT1-K142 methylation probably enhances the membrane translocation of AKT1,and subsequent PDK1 interacts with methylated AKT1 promotes the activation of AKT1.Moreover,JMJD8 knockdown enhanced cell invasion and migration partially by the interaction of JMJD2B with SETDB1-mediated methylated AKT1 K142,which contributed to the induction of AKT1-mediated β-catenin phosphorylation.Thus,our findings unravel a novel role for the JMJD8 in modulating AKT post-translation modification and highlight the histone demethylase JMJD8 would be a potential target for tumor treatment.These results revealed the important role of histone demethylase JMJD8 in regulating cell proliferation,DNA damage repair and tumor metastasis,which provided a new marker and drug target for early diagnosis and treatment of tumors. |
