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Yiguo Zhang - One of the best experts on this subject based on the ideXlab platform.
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activation of the membrane bound Nrf1 Transcription Factor by usp19 a ubiquitin specific protease c terminally tail anchored in the endoplasmic reticulum
bioRxiv, 2021Co-Authors: Yuancai Xiang, Lu Qiu, Meng Wang, Yiguo ZhangAbstract:The membrane-bound Transcription Factor Nrf1 (i.e., encoded by Nfe2l1) is activated by sensing glucose deprivation, cholesterol excess, proteasomal inhibition and oxidative stress, and then mediates distinct signaling responses in order to maintain cellular homeostasis. Herein, we found that Nrf1 stability and transactivity are both enhanced by USP19, a ubiquitin-specific protease tail-anchored in the endoplasmic reticulum (ER) through its C-terminal transmembrane domain. Further experiments revealed that USP19 directly interacts with Nrf1 in proximity to the ER and topologically acts as a deubiquitinating enzyme to remove ubiquitin moieties from this protein, and hence allows it to circumvent the potential proteasomal degradation. Such USP19-mediated effect takes place only after Nrf1 is retrotranslocated by p97 out of ER membranes to dislocate the cytoplasmic side. Conversely, knockout of USP19 causes significant decreases in the Nrf1 abundance and its active isoform entering the nucleus, resulting in down-regulation of its target proteasomal subunits. This led to a modest reduction of USP19-/-derived tumor growth in xenograft mice, when compared with wild-type controls. Altogether, these demonstrate that USP19 serves as a novel mechanistic modulator of Nrf1, but not Nrf2, enabling Nrf1 to be rescued from putative ubiquitin-directed ER-associated degradation pathway. In turn, our additional experimental evidence has unraveled that Transcriptional expression of endogenous USP19 and its promoter-driven reporter genes is differentially regulated by Nrf2, as well by Nrf1, at distinct layers within a complex hierarchical regulatory network.
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Activation of the membrane-bound Nrf1 Transcription Factor by USP19, a tail-anchored ubiquitin-specific protease in the endoplasmic reticulum
2020Co-Authors: Hu Shaofan, Xiang Yuancai, Wang Meng, Yiguo ZhangAbstract:The membrane-bound Transcription Factor Nrf1 (i.e., encoded by Nfe2l1) is activated by sensing glucose deprivation, cholesterol excess, proteasomal inhibition and oxidative stress, and then mediates distinct signaling responses in order to maintain cellular homeostasis. Here, we found that Nrf1 stability and transactivity are enhanced by USP19, a tail-anchored ubiquitin-specific protease in the endoplasmic reticulum (ER). Further experiments revealed that USP19 directly interacts with Nrf1 in proximity to the ER and acts as a deubiquitinating enzyme to remove ubiquitin moieties from this protein and hence circumvent potential proteasomal degradation. Such USP19-mediated effect takes place only after Nrf1 is retrotranslocated by p97 out of ER membranes. Conversely, knockout of USP19 causes significant decreases in Nrf1 abundance and its active isoform entering the nucleus, resulting in down-regulation of its target proteasomal subunits. This led to a modest reduction of USP19-/--derived tumor growth in xenograft mice, when compared with wild-type controls. Altogether, these demonstrate that USP19 serves as a novel mechanistic modulator of Nrf1, but not Nrf2. In turn, our additional evidence has also unraveled that Transcriptional expression of endogenous USP19 and its promoter-driven reporter genes is regulated by Nrf2, as well by Nrf1, at distinct layers within a complex hierarchical regulatory network.
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The selective post-translational processing of Transcription Factor Nrf1 yields distinct isoforms that dictate its ability to differentially regulate gene expression.
Scientific reports, 2015Co-Authors: Yiguo Zhang, Lu Qiu, Yuancai Xiang, Huakan Zhao, John D HayesAbstract:Upon translation, the N-terminal homology box 1 (NHB1) signal anchor sequence of Nrf1 integrates it within the endoplasmic reticulum (ER) whilst its transactivation domains [TADs, including acidic domain 1 (AD1), the flanking Asn/Ser/Thr-rich (NST) domain and AD2] are transiently translocated into the ER lumen, whereupon the NST domain is glycosylated to yield an inactive 120-kDa glycoprotein. Subsequently, these TADs are retrotranslocated into extra-luminal subcellular compartments, where Nrf1 is deglycosylated to yield an active 95-kDa isoform. Herein, we report that AD1 and AD2 are required for the stability of the 120-kDa Nrf1 glycoprotein, but not that of the non-glycosylated/de-glycosylated 95-kDa isoform. Degrons within AD1 do not promote proteolytic degradation of the 120-kDa Nrf1 glycoprotein. However, repositioning of AD2-adjoining degrons (i.e. DSGLS-containing SDS1 and PEST2 sequences) into the cyto/nucleoplasm enables selective topovectorial processing of Nrf1 by the proteasome and/or calpains to generate a cleaved active 85-kDa Nrf1 or a dominant-negative 36-kDa Nrf1γ. Production of Nrf1γ is abolished by removal of SDS1 or PEST2 degrons, whereas production of the cleaved 85-kDa Nrf1 is blocked by deletion of the ER luminal-anchoring NHB2 sequence (aa 81–106). Importantly, Nrf1 activity is positively and/or negatively regulated by distinct doses of proteasome and calpain inhibitors.
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Transcription Factor Nrf1 is negatively regulated by its O-GlcNAcylation status
FEBS letters, 2015Co-Authors: Jiayu Chen, Xiping Liu, Xinping Liu, Yonggang Ren, Libo Yao, Yiguo ZhangAbstract:O-Linked N-acetylglucosamine transferase (OGT) was identified as an Nrf1-interacting protein. Herein, we show that Nrf1 enables interaction with OGT and their co-immunoprecipitates are O-GlcNAcylated by the enzyme. The putative O-GlcNAcylation negatively regulates Nrf1/TCF11 to reduce both its protein stability and transactivation activity of target gene expression. The turnover of Nrf1 is enhanced upon overexpression of OGT, which promotes ubiquitination of the CNC-bZIP protein. Furthermore, the serine/theorine-rich sequence of PEST2 degron within Nrf1 is identified to be involved in the protein O-GlcNAcylation by OGT. Overall, Nrf1 is negatively regulated by its O-GlcNAcylation status that depends on the glucose concentrations.
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Transcription Factor Nrf1 Is topologically repartitioned across membranes to enable target gene transactivation through Its acidic glucose-responsive domains
PloS one, 2014Co-Authors: Yiguo Zhang, Yonggang Ren, John D HayesAbstract:The membrane-bound Nrf1 Transcription Factor regulates critical homeostatic and developmental genes. The conserved N-terminal homology box 1 (NHB1) sequence in Nrf1 targets the cap‘n’collar (CNC) basic basic-region leucine zipper (bZIP) Factor to the endoplasmic reticulum (ER), but it is unknown how its activity is controlled topologically within membranes. Herein, we report a hitherto unknown mechanism by which the transactivation activity of Nrf1 is controlled through its membrane-topology. Thus after Nrf1 is anchored within ER membranes, its acidic transactivation domains (TADs), including the Asn/Ser/Thr-rich (NST) glycodomain situated between acidic domain 1 (AD1) and AD2, are transiently translocated into the lumen of the ER, where NST is glycosylated in the presence of glucose to yield an inactive 120-kDa Nrf1 glycoprotein. Subsequently, portions of the TADs partially repartition across membranes into the cyto/nucleoplasmic compartments, whereupon an active 95-kDa form of Nrf1 accumulates, a process that is more obvious in glucose-deprived cells and may involve deglycosylation. The repartitioning of Nrf1 out of membranes is monitored within this protein by its acidic-hydrophobic amphipathic glucose-responsive domains, particularly the Neh5L subdomain within AD1. Therefore, the membrane-topological organization of Nrf1 dictates its post-translational modifications (i.e. glycosylation, the putative deglycosylation and selective proteolysis), which together control its ability to transactivate target genes.
Jefferson Y Chan - One of the best experts on this subject based on the ideXlab platform.
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the deubiquitinating enzyme usp7 regulates the Transcription Factor Nrf1 by modulating its stability in response to toxic metal exposure
Journal of Biological Chemistry, 2021Co-Authors: John Jw Han, Hyun M Kim, Jun Y Lee, Yerin S Jeon, Jefferson Y ChanAbstract:The Nuclear Factor E2-related Factor 1 (Nrf1) Transcription Factor performs a critical role in regulating cellular homeostasis as part of the cellular stress response, and drives the expression of antioxidants and detoxification enzymes among many other functions. Ubiquitination plays an important role in controlling the abundance and thus nuclear accumulation of Nrf1 proteins, but the regulatory enzymes that act on Nrf1 are not fully defined. Here, we identified ubiquitin specific protease 7 (USP7), a deubiquitinating enzyme, as a novel regulator of Nrf1 activity. We found that USP7 interacts with Nrf1a and TCF11-the two long protein isoforms of Nrf1. Expression of wild type USP7, but not its catalytically defective mutant, resulted in decreased ubiquitination of TCF11 and Nrf1a, leading to their increased stability, and increased transactivation of reporter gene expression by TCF11 and Nrf1a. In contrast, knockdown or pharmacologic inhibition of USP7 dramatically increased ubiquitination of TCF11 and Nrf1a, and reduction of their steady state levels. Loss of USP7 function attenuated the induction of Nrf1 protein expression in response to treatment with arsenic and other toxic metals, and inhibition of USP7 activity significantly sensitized cells to arsenic treatment. Collectively, these findings suggest that USP7 may act to modulate abundance of Nrf1 protein to induce gene expression in response to toxic metal exposure.
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deficiency in the nuclear related Factor erythroid 2 Transcription Factor Nrf1 leads to genetic instability
FEBS Journal, 2012Co-Authors: Diamanda Rigas, Ara Cho, Jefferson Y ChanAbstract:Nuclear Factor erythroid-derived 2-related Factor 1 (Nrf1) regulates cellular stress response genes, and has also been suggested to play a role in other cellular processes. We previously demonstrated that hepatocyte-specific deletion of Nrf1 in mice resulted in spontaneous apoptosis, inflammation, and development of liver tumors. Here, we showed that both fibroblasts derived from Nrf1 null mouse embryos and fibroblasts expressing a conditional Nrf1 allele showed increased micronuclei and formation of abnormal nuclei. Lentiviral shRNA-mediated knockdown of Nrf1 in SAOS–2 cells also resulted in increased micronuclei, abnormal mitosis and multi-nucleated cells. Metaphase analyses showed increased aneuploidy in Nrf1−/− embryonic fibroblasts. Nuclear defects in Nrf1-deficient cells were associated with decreased expression of various genes encoding kinetochore and mitotic checkpoint proteins. Our findings suggest that Nrf1 may play a role in maintaining genomic integrity, and that Nrf1 dysregulation may induce tumorigenesis.
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gsk3 negatively regulates stress response mediated by Transcription Factor Nrf1 resulting in increased neuronal apoptosis and neurodegeneration
The FASEB Journal, 2012Co-Authors: Madhurima Biswas, Jefferson Y ChanAbstract:Oxidative and endoplasmic reticulum (ER) stress play an important role in the pathogenesis of neurodegenerative diseases. Nuclear Factor E2-related Factor 1 (Nrf1), a member of the Cap n Collar bas...
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Transcription Factor Nrf1 mediates the proteasome recovery pathway after proteasome inhibition in mammalian cells
Molecular Cell, 2010Co-Authors: Senthil K. Radhakrishnan, Jefferson Y Chan, Candy Lee, Raymond J. Deshaies, Patrick Young, Anne BeskowAbstract:In Saccharomyces cerevisiae, chemical or genetic inhibition of proteasome activity induces new proteasome synthesis promoted by the Transcription Factor RPN4. This ensures that proteasome activity is matched to demand. This Transcriptional feedback loop is conserved in mammals, but its molecular basis is not understood. Here, we report that nuclear Factor erythroid-derived 2-related Factor 1 (Nrf1), a Transcription Factor of the cap “n” collar basic leucine zipper family, but not the related Nrf2, is necessary for induced proteasome gene Transcription in mouse embryonic fibroblasts (MEFs). Promoter-reporter assays revealed the importance of antioxidant response elements in Nrf1-mediated upregulation of proteasome subunit genes. Nrf1^(−/−) MEFs were impaired in the recovery of proteasome activity after transient treatment with the covalent proteasome inhibitor YU101, and knockdown of Nrf1 in human cancer cells enhanced cell killing by YU101. Taken together, our results suggest that Nrf1-mediated proteasome homeostasis could be an attractive target for therapeutic intervention in cancer.
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liver specific inactivation of the Nrf1 gene in adult mouse leads to nonalcoholic steatohepatitis and hepatic neoplasia
Proceedings of the National Academy of Sciences of the United States of America, 2005Co-Authors: Zhenrong Xu, Linyun Chen, Laura Leung, Jefferson Y ChanAbstract:Knockout studies have shown that the Transcription Factor Nrf1 is essential for embryonic development. Nrf1 has been implicated to play a role in mediating activation of oxidative stress response genes through the antioxidant response element (ARE). Because of embryonic lethality in knockout mice, analysis of this function in the adult knockout mouse was not possible. We report here that mice with somatic inactivation of Nrf1 in the liver developed hepatic cancer. Before cancer development, mutant livers exhibited steatosis, apoptosis, necrosis, inflammation, and fibrosis. In addition, hepatocytes lacking Nrf1 showed oxidative stress, and gene expression analysis showed decreased expression of various ARE-containing genes, and up-regulation of CYP4A genes. These results suggest that reactive oxygen species generated from CYP4A-mediated fatty acid oxidation work synergistically with diminished expression of ARE-responsive genes to cause oxidative stress in mutant hepatocytes. Thus, Nrf1 has a protective function against oxidative stress and, potentially, a function in lipid homeostasis in the liver. Because the phenotype is similar to nonalcoholic steatohepatitis, these animals may prove useful as a model for investigating molecular mechanisms of nonalcoholic steatohepatitis and liver cancer.
John D Hayes - One of the best experts on this subject based on the ideXlab platform.
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The selective post-translational processing of Transcription Factor Nrf1 yields distinct isoforms that dictate its ability to differentially regulate gene expression.
Scientific reports, 2015Co-Authors: Yiguo Zhang, Lu Qiu, Yuancai Xiang, Huakan Zhao, John D HayesAbstract:Upon translation, the N-terminal homology box 1 (NHB1) signal anchor sequence of Nrf1 integrates it within the endoplasmic reticulum (ER) whilst its transactivation domains [TADs, including acidic domain 1 (AD1), the flanking Asn/Ser/Thr-rich (NST) domain and AD2] are transiently translocated into the ER lumen, whereupon the NST domain is glycosylated to yield an inactive 120-kDa glycoprotein. Subsequently, these TADs are retrotranslocated into extra-luminal subcellular compartments, where Nrf1 is deglycosylated to yield an active 95-kDa isoform. Herein, we report that AD1 and AD2 are required for the stability of the 120-kDa Nrf1 glycoprotein, but not that of the non-glycosylated/de-glycosylated 95-kDa isoform. Degrons within AD1 do not promote proteolytic degradation of the 120-kDa Nrf1 glycoprotein. However, repositioning of AD2-adjoining degrons (i.e. DSGLS-containing SDS1 and PEST2 sequences) into the cyto/nucleoplasm enables selective topovectorial processing of Nrf1 by the proteasome and/or calpains to generate a cleaved active 85-kDa Nrf1 or a dominant-negative 36-kDa Nrf1γ. Production of Nrf1γ is abolished by removal of SDS1 or PEST2 degrons, whereas production of the cleaved 85-kDa Nrf1 is blocked by deletion of the ER luminal-anchoring NHB2 sequence (aa 81–106). Importantly, Nrf1 activity is positively and/or negatively regulated by distinct doses of proteasome and calpain inhibitors.
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Transcription Factor Nrf1 Is topologically repartitioned across membranes to enable target gene transactivation through Its acidic glucose-responsive domains
PloS one, 2014Co-Authors: Yiguo Zhang, Yonggang Ren, John D HayesAbstract:The membrane-bound Nrf1 Transcription Factor regulates critical homeostatic and developmental genes. The conserved N-terminal homology box 1 (NHB1) sequence in Nrf1 targets the cap‘n’collar (CNC) basic basic-region leucine zipper (bZIP) Factor to the endoplasmic reticulum (ER), but it is unknown how its activity is controlled topologically within membranes. Herein, we report a hitherto unknown mechanism by which the transactivation activity of Nrf1 is controlled through its membrane-topology. Thus after Nrf1 is anchored within ER membranes, its acidic transactivation domains (TADs), including the Asn/Ser/Thr-rich (NST) glycodomain situated between acidic domain 1 (AD1) and AD2, are transiently translocated into the lumen of the ER, where NST is glycosylated in the presence of glucose to yield an inactive 120-kDa Nrf1 glycoprotein. Subsequently, portions of the TADs partially repartition across membranes into the cyto/nucleoplasmic compartments, whereupon an active 95-kDa form of Nrf1 accumulates, a process that is more obvious in glucose-deprived cells and may involve deglycosylation. The repartitioning of Nrf1 out of membranes is monitored within this protein by its acidic-hydrophobic amphipathic glucose-responsive domains, particularly the Neh5L subdomain within AD1. Therefore, the membrane-topological organization of Nrf1 dictates its post-translational modifications (i.e. glycosylation, the putative deglycosylation and selective proteolysis), which together control its ability to transactivate target genes.
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Identification of topological determinants in the N-terminal domain of Transcription Factor Nrf1 that control its orientation in the endoplasmic reticulum membrane.
The Biochemical journal, 2010Co-Authors: Yiguo Zhang, John D HayesAbstract:Nrf1 [NF-E2 (nuclear Factor-erythroid 2)-related Factor 1] is a CNC (cap'n'collar) bZIP (basic-region leucine zipper) Transcription Factor that is tethered to ER (endoplasmic reticulum) and nuclear envelope membranes through its N-terminal signal peptide (residues 1-30). Besides the signal peptide, amino acids 31-90 of Nrf1 also negatively regulate the CNC-bZIP Factor. In the present study we have tested the hypothesis that amino acids 31-90 of Nrf1, and the overlapping NHB2 (N-terminal homology box 2; residues 82-106), inhibit Nrf1 because they control its topology within membranes. This region contains three amphipathic alpha-helical regions comprising amino acids 31-50 [called the SAS (signal peptide-associated sequence)], 55-82 [called the CRACs (cholesterol-recognition amino acid consensus sequences)] and 89-106 (part of NHB2). We present experimental data showing that the signal peptide of Nrf1 contains a TM1 (transmembrane 1) region (residues 7-24) that is orientated across the ER membrane in an N(cyt)/C(lum) fashion with its N-terminus facing the cytoplasm and its C-terminus positioned in the lumen of the ER. Once Nrf1 is anchored to the ER membrane through TM1, the remaining portion of the N-terminal domain (NTD, residues 1-124) is transiently translocated into the ER lumen. Thereafter, Nrf1 adopts a topology in which the SAS is inserted into the membrane, the CRACs are probably repartitioned to the cytoplasmic side of the ER membrane, and NHB2 may serve as an anchor switch, either lying on the luminal surface of the ER or traversing the membrane with an N(cyt)/C(lum) orientation. Thus Nrf1 can adopt several topologies within membranes that are determined by its NTD.
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the nhb1 n terminal homology box 1 sequence in Transcription Factor Nrf1 is required to anchor it to the endoplasmic reticulum and also to enable its asparagine glycosylation
Biochemical Journal, 2007Co-Authors: Yiguo Zhang, Masayuki Yamamoto, John M Lucocq, John D HayesAbstract:Nrf1 (nuclear Factor-erythroid 2 p45 subunit-related Factor 1) is negatively controlled by its NTD (N-terminal domain) that lies between amino acids 1 and 124. This domain contains a leucine-rich sequence, called NHB1 (N-terminal homology box 1; residues 11–30), which tethers Nrf1 to the ER (endoplasmic reticulum). Electrophoresis resolved Nrf1 into two major bands of approx. 95 and 120 kDa. The 120-kDa Nrf1 form represents a glycosylated protein that was present exclusively in the ER and was converted into a substantially smaller polypeptide upon digestion with either peptide:N-glycosidase F or endoglycosidase H. By contrast, the 95-kDa Nrf1 form did not appear to be glycosylated and was present primarily in the nucleus. NHB1 and its adjacent residues conform to the classic tripartite signal peptide sequence, comprising n-, h- and c-regions. The h-region (residues 11–22), but neither the n-region (residues 1–10) nor the c-region (residues 23–30), is required to direct Nrf1 to the ER. Targeting Nrf1 to the ER is necessary to generate the 120-kDa glycosylated protein. The n-region and c-region are required for correct membrane orientation of Nrf1, as deletion of residues 2–10 or 23–30 greatly increased its association with the ER and the extent to which it was glycosylated. The NHB1 does not contain a signal peptidase cleavage site, indicating that it serves as an ER anchor sequence. Wild-type Nrf1 is glycosylated through its Asn/Ser/Thr-rich domain, between amino acids 296 and 403, and this modification was not observed in an Nrf1Δ299–400 mutant. Glycosylation of Nrf1 was not necessary to retain it in the ER.
Masayuki Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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Transcription Factor Nrf1 negatively regulates the cystine glutamate transporter and lipid metabolizing enzymes
Molecular and Cellular Biology, 2014Co-Authors: Tadayuki Tsujita, Liam Baird, Vivian Peirce, Yuka Matsuyama, Misaki Takaku, Shawn V Walsh, Julian L Griffin, Akira Uruno, Masayuki YamamotoAbstract:Liver-specific Nrf1 (NF-E2-p45-related Factor 1) knockout mice develop nonalcoholic steatohepatitis. To identify postnatal mechanisms responsible for this phenotype, we generated an inducible liver-specific Nrf1 knockout mouse line using animals harboring an Nrf1(flox) allele and a rat CYP1A1-Cre transgene (Nrf1(flox/flox)::CYP1A1-Cre mice). Administration of 3-methylcholanthrene (3-MC) to these mice (Nrf1(flox/flox)::CYP1A1-Cre+3MC mice) resulted in loss of hepatic Nrf1 expression. The livers of mice lacking Nrf1 accumulated lipid, and the hepatic fatty acid (FA) composition in such animals differed significantly from that in the Nrf1(flox/flox)::CYP1A1-Cre control. This change was provoked by upregulation of several FA metabolism genes. Unexpectedly, we also found that the level of glutathione was increased dramatically in livers of Nrf1(flox/flox)::CYP1A1-Cre+3MC mice. While expression of glutathione biosynthetic enzymes was unchanged, xCT, a component of the cystine/glutamate antiporter system x(c)(-), was significantly upregulated in livers of Nrf1(flox/flox)::CYP1A1-Cre+3MC mice, suggesting that Nrf1 normally suppresses xCT. Thus, stress-inducible expression of xCT is a two-step process: under homeostatic conditions, Nrf1 effectively suppresses nonspecific transactivation of xCT, but when cells encounter severe oxidative/electrophilic stress, Nrf1 is displaced from an antioxidant response element (ARE) in the gene promoter while Nrf2 is recruited to the ARE. Thus, Nrf1 controls both the FA and the cystine/cysteine content of hepatocytes by participating in an elaborate regulatory network.
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enzymesand lipid metabolizing regulates the cystine glutamate Transcription Factor Nrf1 negatively
2014Co-Authors: Akira Uruno, Masayuki Yamamoto, Vivian Peirce, Misaki Takaku, Shawn V Walsh, Liam BairdAbstract:rf1 is a member of the CNC-bZIP (Cap’n’Collar basic regionleucine zipper) group of Transcription Factors. Four coremembersofthisfamilyhavebeenidentified,i.e.,NF-E2p45,Nrf1,Nrf2, and Nrf3, along with the two more distantly related mem-bers Bach1 and Bach2 (1, 2). Upon stimulation, the CNC-bZIPFactors heterodimerize in the nucleus with small Maf (sMaf) pro-teins (i.e., MafF, MafK, or MafG) before binding to antioxidantresponse element (ARE)/electrophile response element (EpRE)(TGA[G/C]NNNGC) sequences in the promoters of target genes,many of which exert cytoprotective functions. In addition, sMafproteins can form homodimers that bind to a palindromic ex-tended ARE sequence, called a Maf recognition element (MARE)(TGCTGA[G/C]TCAGCA), and in so doing repress genes in-volved in cell differentiation and organization, such as those forrhodopsin and crystallin (3).It has previously been shown that each CNC-bZIP Factor reg-ulates a different set of genes, despite the fact that their consensusbinding sequences are similar. While NF-E2 p45 and Nrf3 aresubjecttotissue-specificexpression,inhematopoieticcelllineagesand placenta, respectively (4–6), Nrf1 and Nrf2 are essentially ex-pressed ubiquitously (7). Importantly, it has been speculated thatNrf1 and Nrf2 may exhibit combinational or competitive func-tions, but details of the basis for their distinct activities have yet tobe established (7, 8). Furthermore, while full-length Nrf1 transac-tivates ARE-driven gene expression, several short Nrf1 isoformsexist that have been reported to repress ARE-driven genes (9–11),and this may account for some of the differences observed be-tween Nrf1 and Nrf2.Analyses of gene knockout (KO) mouse lines have providedinvaluable information about the physiological function of CNC-bZIP Factors. We and other laboratories have knocked out all ofthe CNC-bZIP Factors, and the phenotypes of the resulting micehave been described (12). Among the knockout mouse lines, onlyNrf1-null mice exhibit embryonic lethality. The majority ofNF-E2 p45 knockout mice die because of bleeding during theneonatal period, whereas Nrf2- and Nrf3-null mice develop nor-mally. Nrf1 deficiency results in hepatocyte dysfunction and im-pairment of early hematopoietic development, leading to death atembryonic day 13.5 (E13.5). Importantly, a similar phenotype isobserved in the
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the nhb1 n terminal homology box 1 sequence in Transcription Factor Nrf1 is required to anchor it to the endoplasmic reticulum and also to enable its asparagine glycosylation
Biochemical Journal, 2007Co-Authors: Yiguo Zhang, Masayuki Yamamoto, John M Lucocq, John D HayesAbstract:Nrf1 (nuclear Factor-erythroid 2 p45 subunit-related Factor 1) is negatively controlled by its NTD (N-terminal domain) that lies between amino acids 1 and 124. This domain contains a leucine-rich sequence, called NHB1 (N-terminal homology box 1; residues 11–30), which tethers Nrf1 to the ER (endoplasmic reticulum). Electrophoresis resolved Nrf1 into two major bands of approx. 95 and 120 kDa. The 120-kDa Nrf1 form represents a glycosylated protein that was present exclusively in the ER and was converted into a substantially smaller polypeptide upon digestion with either peptide:N-glycosidase F or endoglycosidase H. By contrast, the 95-kDa Nrf1 form did not appear to be glycosylated and was present primarily in the nucleus. NHB1 and its adjacent residues conform to the classic tripartite signal peptide sequence, comprising n-, h- and c-regions. The h-region (residues 11–22), but neither the n-region (residues 1–10) nor the c-region (residues 23–30), is required to direct Nrf1 to the ER. Targeting Nrf1 to the ER is necessary to generate the 120-kDa glycosylated protein. The n-region and c-region are required for correct membrane orientation of Nrf1, as deletion of residues 2–10 or 23–30 greatly increased its association with the ER and the extent to which it was glycosylated. The NHB1 does not contain a signal peptidase cleavage site, indicating that it serves as an ER anchor sequence. Wild-type Nrf1 is glycosylated through its Asn/Ser/Thr-rich domain, between amino acids 296 and 403, and this modification was not observed in an Nrf1Δ299–400 mutant. Glycosylation of Nrf1 was not necessary to retain it in the ER.
Hiroaki Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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Possible roles of the Transcription Factor Nrf1 (NFE2L1) in neural homeostasis by regulating the gene expression of deubiquitinating enzymes.
Biochemical and biophysical research communications, 2017Co-Authors: Hiroaki Taniguchi, Tsuyoshi Waku, Kaori Kubo, Shota Okamuro, Misaki Koji, Atsushi Hatanaka, Yimeng Sun, A.m. Masudul Azad Chowdhury, Akiyoshi Fukamizu, Akira KobayashiAbstract:The Transcription Factor Nrf1 (NFE2L1) maintains protein homeostasis (proteostasis) by regulating the gene expression of proteasome subunits in response to proteasome inhibition. The deletion of the Nrf1 gene in neural stem/progenitor cells causes severe neurodegeneration due to the accumulation of ubiquitinated proteins in Purkinje cells and motor neurons (Nrf1 NKO mice). However, the molecular mechanisms governing this neurodegenerative process remain unclear. We demonstrate herein that the loss of Nrf1 leads to the reduced gene expression of the deubiquitinating enzymes (DUBs) but not proteasome subunits in Nrf1 NKO mice between P7 and P18. First, we show that K48-linked polyubiquitinated proteins accumulate in Nrf1-deficient Purkinje cells and cerebral cortex neurons. Nevertheless, loss of Nrf1 does not alter the expression and proteolytic activity of proteasome. A significantly reduced expression of deubiquitinating enzymes was also demonstrated in Nrf1-deficient cerebellar tissue using microarray analysis. The genome database further reveals species-conserved ARE, a Nrf1 recognition element, in the regulatory region of certain DUB genes. Furthermore, we show that Nrf1 can activate Usp9x gene expression related to neurodegeneration. Altogether these findings suggest that neurodegeneration in Nrf1 NKO mice may stem from the dysfunction of the ubiquitin-mediated regulation of neuronal proteins.
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usp15 stabilizes the Transcription Factor Nrf1 in the nucleus promoting the proteasome gene expression
Biochemical and Biophysical Research Communications, 2016Co-Authors: Kousuke Fukagai, Hiroki Kato, Tsuyoshi Waku, A Masudul Azad M Chowdhury, Fuminori Tsuruta, Tomoki Chiba, Kaori Kubo, Tohru Natsume, Mariko Matsumoto, Hiroaki TaniguchiAbstract:The Transcriptional Factor Nrf1 (NF-E2-related Factor 1) sustains protein homeostasis (proteostasis) by regulating the expression of proteasome genes. Under physiological conditions, the Transcriptional activity of Nrf1 is repressed by its sequestration into the endoplasmic reticulum (ER) and furthermore by two independent ubiquitin-proteasome pathways, comprising Hrd1 and β-TrCP in the cytoplasm and nucleus, respectively. However, the molecular mechanisms underlying Nrf1 activation remain unclear. Here, we report that USP15 (Ubiquitin-Specific Protease 15) activates Nrf1 in the nucleus by stabilizing it through deubiquitination. We first identified USP15 as an Nrf1-associated Factor through proteome analysis. USP15 physically interacts with Nrf1, and it markedly stabilizes Nrf1 by removing its ubiquitin moieties. USP15 activates the Nrf1-mediated expression of a proteasome gene luciferase reporter and endogenous proteasome activity. The siRNA-mediated knockdown of USP15 diminishes the Nrf1-induced proteasome gene expression in response to proteasome inhibition. These results uncover a new regulatory mechanism that USP15 activates Nrf1 against the β-TrCP inhibition to maintain proteostasis.