Faithful segregation of mitotic chromosomes requires bi-orientation of sister chromatids, which relies on the sensing of correct attachments between spindle microtubules and kinetochores. Although the mechanisms under...Faithful segregation of mitotic chromosomes requires bi-orientation of sister chromatids, which relies on the sensing of correct attachments between spindle microtubules and kinetochores. Although the mechanisms underlying PLK1 activation have been extensively studied, the regulatory mechanisms that couple PLK1 activity to accurate chromosome segregation are not well understood. In particular, PLK1 is implicated in stabilizing kinetochore–microtubule attachments, but how kinetochore PLK1 activity is regulated to avoid hyperstabilized kinetochore–microtubules in mitosis remains elusive. Here, we show that kinetochore PLK1 kinase activity is modulated by SET7/9 via lysine methylation during early mitosis. The SET7/9-elicited dimethylation occurs at the Lys191 of PLK1, which tunes down its activity by limiting ATP utilization. Overexpression of the non-methylatable PLK1 mutant or chemical inhibition of SET7/9 methyltransferase activity resulted in mitotic arrest due to destabilized kinetochore–microtubule attachments. These data suggest that kinetochore PLK1 is essential for stable kinetochore–microtubule attachments and methylation by SET7/9 promotes dynamic kinetochore–microtubule attachments for accurate error correction. Our findings define a novel homeostatic regulation at the kinetochore that integrates protein phosphorylation and methylation with accurate chromosome segregation for maintenance of genomic stability.展开更多
Background and Aims:Multiple regulatory mechanisms play an important role in arsenic-induced liver injury.To investigate whether histone H3 lysine 4(H3K4)methyltransferase(SET7/9)and histone H3K4 demethyltransferase(L...Background and Aims:Multiple regulatory mechanisms play an important role in arsenic-induced liver injury.To investigate whether histone H3 lysine 4(H3K4)methyltransferase(SET7/9)and histone H3K4 demethyltransferase(LSD1/KDM1A)can regulate endoplasmic reticulum stress(ERS)-related apoptosis by modulating the changes of H3K4 methylations in liver cells treated with arsenic.Methods:Apoptosis,proliferation and cell cycles were quantified by flow cytometry and real-time cell analyzer.The expression of ERS-and epigenetic-related proteins was detected by Western blot analysis.The antisense SET7/9 expression vector and the overexpressed LSD1 plasmid were used for transient transfection of LO_(2) cells.The effects of NaAsO_(2) on the methylation of H3 in the promoter regions of 78 kDa glucose-regulated protein,activating transcription factor 4 and C/EBP-homologous protein were evaluated by chromatin immunoprecipitation assay.Results:The protein expression of LSD1(1.25±0.08 vs.1.77±0.08,p=0.02)was markedly decreased by treatment with 100μM NaAsO_(2),whereas the SET7/9(0.68±0.05 vs.1.10±0.13,p=0.002)expression level was notably increased,which resulted in increased H3K4me1/2(0.93±0.64,1.19±0.22 vs.0.71±0.13,0.84±0.13,p=0.03 and p=0.003).After silencing SET7/9 and overexpressing LSD1 by transfection,apoptosis rate(in percentage:3.26±0.34 vs.7.04±0.42,4.80±0.32 vs.7.52±0.38,p=0.004 and p=0.02)was significantly decreased and proliferation rate was notably increased,which is reversed after inhibiting LSD1(in percentage:9.31±0.40 vs.7.52±0.38,p=0.03).Furthermore,the methylation levels of H3 in the promoter regions of GRP78(20.80±2.40 vs.11.75±2.47,20.46±2.23 vs.14.37±0.91,p=0.03 and p=0.01)and CHOP(48.67±4.04 vs.16.67±7.02,59.33±4.51 vs.20.67±3.06,p=0.004 and p=0.001)were significantly increased in LO_(2) cells exposed to 100μM NaAsO_(2) for 24 h.Conclusions:Histone methyltransferase SET7/9 and histone demethyltransferase LSD1 jointly regulate the changes of H3K4me1/me2 levels in arsenic-induced apoptosis.NaAsO_(2) induces apoptosis in LO_(2) cells by activating the ERS-mediated apoptotic signaling pathway,at least partially by enhancing the methylation of H3 on the promoter regions of ERS-associated genes,including GRP78 and CHOP.展开更多
缺氧诱导因子-1(hypoxia-inducible factor-1,HIF-1)在低氧应答中起着关键作用。HIF-1是由HIF-1α和HIF-1β两种亚基组成的异二聚体转录因子。该研究探讨了缺氧条件下,泛素样含PHD和环指域1(ubiquitin-like with PHD and RING finger do...缺氧诱导因子-1(hypoxia-inducible factor-1,HIF-1)在低氧应答中起着关键作用。HIF-1是由HIF-1α和HIF-1β两种亚基组成的异二聚体转录因子。该研究探讨了缺氧条件下,泛素样含PHD和环指域1(ubiquitin-like with PHD and RING finger domains 1,UHRF1)对HIF-1α蛋白水平的影响。利用UHRF1靶向小干扰RNA抑制UHRF1的表达后,分别通过Western blot和q RT-PCR检测HIF-1α蛋白及m RNA的表达水平。在He La和Hep G2细胞中过表达UHRF1,通过Western blot检测HIF-1α的蛋白表达水平。同时过表达或抑制包含SET结构域的组蛋白甲基转移酶7/9(SET domain containing histone lysine methyltransferase 7/9,SET7/9)及UHRF1,用Western blot检测HIF-1α蛋白表达水平。利用免疫共沉淀的方法检测UHRF1及其不同截短蛋白与HIF-1α蛋白之间的相互作用。将UHRF1的第385位赖氨酸突变为精氨酸,利用免疫共沉淀检测该突变蛋白与HIF-1α蛋白之间的相互作用。研究发现,在低氧条件下,抑制UHRF1的表达能够上调HIF-1α的蛋白水平,且不影响HIF-1α的m RNA水平;单独过表达UHRF1并不影响HIF-1α的蛋白水平,但是当同时过表达UHRF1和SET7/9时,HIF-1α蛋白水平降低;并且同时抑制UHRF1和SET7/9的表达会挽救单独抑制UHRF1表达时HIF-1α蛋白水平增加的现象。进一步发现,UHRF1和HIF-1α蛋白相互作用,两者之间的相互作用关系依赖于UHRF1的第385位赖氨酸甲基修饰,且该甲基化修饰受到SET7/9的调控。UHRF1可依赖SET7/9介导的自身蛋白甲基化修饰与HIF-1α相互作用,并影响HIF-1α的蛋白水平。展开更多
基金This work was supported in part by the National Natural Science Foundation of China(31430054,31320103904,31621002,31671405,91854203,91853115,21922706,31671407,31871359,31601097,and 21672201)the National Key Research and Development Program of China(2017YFA0503600 and 2016YFA0100500)+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDB19000000)Chinese Academy of Sciences Center for Excellence in Molecular Cell Science(2015HSC-UE010)MOE Innovative Team(IRT_17R102),and the US National Institutes of Health(CA164133and DK26929).
文摘Faithful segregation of mitotic chromosomes requires bi-orientation of sister chromatids, which relies on the sensing of correct attachments between spindle microtubules and kinetochores. Although the mechanisms underlying PLK1 activation have been extensively studied, the regulatory mechanisms that couple PLK1 activity to accurate chromosome segregation are not well understood. In particular, PLK1 is implicated in stabilizing kinetochore–microtubule attachments, but how kinetochore PLK1 activity is regulated to avoid hyperstabilized kinetochore–microtubules in mitosis remains elusive. Here, we show that kinetochore PLK1 kinase activity is modulated by SET7/9 via lysine methylation during early mitosis. The SET7/9-elicited dimethylation occurs at the Lys191 of PLK1, which tunes down its activity by limiting ATP utilization. Overexpression of the non-methylatable PLK1 mutant or chemical inhibition of SET7/9 methyltransferase activity resulted in mitotic arrest due to destabilized kinetochore–microtubule attachments. These data suggest that kinetochore PLK1 is essential for stable kinetochore–microtubule attachments and methylation by SET7/9 promotes dynamic kinetochore–microtubule attachments for accurate error correction. Our findings define a novel homeostatic regulation at the kinetochore that integrates protein phosphorylation and methylation with accurate chromosome segregation for maintenance of genomic stability.
基金The present study was supported by the National Natural Science Foundation of China(Grant No.81100284)Guizhou Science and Technology Cooperation Platform Personnel[2018](Grant No.5779-10,5779-19)Science and Technology Foundation of Guizhou Province(Grant No.ZK[2021]-364)。
文摘Background and Aims:Multiple regulatory mechanisms play an important role in arsenic-induced liver injury.To investigate whether histone H3 lysine 4(H3K4)methyltransferase(SET7/9)and histone H3K4 demethyltransferase(LSD1/KDM1A)can regulate endoplasmic reticulum stress(ERS)-related apoptosis by modulating the changes of H3K4 methylations in liver cells treated with arsenic.Methods:Apoptosis,proliferation and cell cycles were quantified by flow cytometry and real-time cell analyzer.The expression of ERS-and epigenetic-related proteins was detected by Western blot analysis.The antisense SET7/9 expression vector and the overexpressed LSD1 plasmid were used for transient transfection of LO_(2) cells.The effects of NaAsO_(2) on the methylation of H3 in the promoter regions of 78 kDa glucose-regulated protein,activating transcription factor 4 and C/EBP-homologous protein were evaluated by chromatin immunoprecipitation assay.Results:The protein expression of LSD1(1.25±0.08 vs.1.77±0.08,p=0.02)was markedly decreased by treatment with 100μM NaAsO_(2),whereas the SET7/9(0.68±0.05 vs.1.10±0.13,p=0.002)expression level was notably increased,which resulted in increased H3K4me1/2(0.93±0.64,1.19±0.22 vs.0.71±0.13,0.84±0.13,p=0.03 and p=0.003).After silencing SET7/9 and overexpressing LSD1 by transfection,apoptosis rate(in percentage:3.26±0.34 vs.7.04±0.42,4.80±0.32 vs.7.52±0.38,p=0.004 and p=0.02)was significantly decreased and proliferation rate was notably increased,which is reversed after inhibiting LSD1(in percentage:9.31±0.40 vs.7.52±0.38,p=0.03).Furthermore,the methylation levels of H3 in the promoter regions of GRP78(20.80±2.40 vs.11.75±2.47,20.46±2.23 vs.14.37±0.91,p=0.03 and p=0.01)and CHOP(48.67±4.04 vs.16.67±7.02,59.33±4.51 vs.20.67±3.06,p=0.004 and p=0.001)were significantly increased in LO_(2) cells exposed to 100μM NaAsO_(2) for 24 h.Conclusions:Histone methyltransferase SET7/9 and histone demethyltransferase LSD1 jointly regulate the changes of H3K4me1/me2 levels in arsenic-induced apoptosis.NaAsO_(2) induces apoptosis in LO_(2) cells by activating the ERS-mediated apoptotic signaling pathway,at least partially by enhancing the methylation of H3 on the promoter regions of ERS-associated genes,including GRP78 and CHOP.
