title: The C-terminal domain of Nrf1 negatively regulates the full-length CNC-bZIP factor and its shorter isoform LCR-F1/Nrf1β; both are also inhibited by the small dominant-negative Nrf1γ/δ isoforms that down-regulate ARE-battery gene expression.
abstract: The C-terminal domain (CTD, aa 686-741) of nuclear factor-erythroid 2 p45-related factor 1 (Nrf1) shares 53% amino acid sequence identity with the equivalent Neh3 domain of Nrf2, a homologous transcription factor. The Neh3 positively regulates Nrf2, but whether the Neh3-like (Neh3L) CTD of Nrf1 has a similar role in regulating Nrf1-target gene expression is unknown. Herein, we report that CTD negatively regulates the full-length Nrf1 (i.e. 120-kDa glycoprotein and 95-kDa deglycoprotein) and its shorter isoform LCR-F1/Nrf1β (55-kDa). Attachment of its CTD-adjoining 112-aa to the C-terminus of Nrf2 yields the chimaeric Nrf2-C112Nrf1 factor with a markedly decreased activity. Live-cell imaging of GFP-CTD reveals that the extra-nuclear portion of the fusion protein is allowed to associate with the endoplasmic reticulum (ER) membrane through the amphipathic Neh3L region of Nrf1 and its basic c-tail. Thus removal of either the entire CTD or the essential Neh3L portion within CTD from Nrf1, LCR-F1/Nrf1β and Nrf2-C112Nrf1, results in an increase in their transcriptional ability to regulate antioxidant response element (ARE)-driven reporter genes. Further examinations unravel that two smaller isoforms, 36-kDa Nrf1γ and 25-kDa Nrf1δ, act as dominant-negative inhibitors to compete against Nrf1, LCR-F1/Nrf1β and Nrf2. Relative to Nrf1, LCR-F1/Nrf1β is a weak activator, that is positively regulated by its Asn/Ser/Thr-rich (NST) domain and acidic domain 2 (AD2). Like AD1 of Nrf1, both AD2 and NST domain of LCR-F1/Nrf1β fused within two different chimaeric contexts to yield Gal4D:Nrf1β607 and Nrf1β:C270Nrf2, positively regulate their transactivation activity of cognate Gal4- and Nrf2-target reporter genes. More importantly, differential expression of endogenous ARE-battery genes is attributable to up-regulation by Nrf1 and LCR-F1/Nrf1β and down-regulation by Nrf1γ and Nrf1δ.
authors.affiliation: The Laboratory of Cell Biochemistry and Gene Regulation, College of Medical Bioengineering and Faculty of Life Sciences, Chongqing University, Shapingba District, Chongqing, China.
authors.forename: Yiguo
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: The Laboratory of Cell Biochemistry and Gene Regulation, College of Medical Bioengineering and Faculty of Life Sciences, Chongqing University, Shapingba District, Chongqing, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Qiu
authors.affiliation: The Laboratory of Cell Biochemistry and Gene Regulation, College of Medical Bioengineering and Faculty of Life Sciences, Chongqing University, Shapingba District, Chongqing, China.
authors.forename: Shaojun
authors.initials: S
authors.lastname: Li
authors.affiliation: The Laboratory of Cell Biochemistry and Gene Regulation, College of Medical Bioengineering and Faculty of Life Sciences, Chongqing University, Shapingba District, Chongqing, China.
authors.forename: Yuancai
authors.initials: Y
authors.lastname: Xiang
authors.affiliation: The Laboratory of Cell Biochemistry and Gene Regulation, College of Medical Bioengineering and Faculty of Life Sciences, Chongqing University, Shapingba District, Chongqing, China.
authors.forename: Jiayu
authors.initials: J
authors.lastname: Chen
authors.affiliation: The Laboratory of Cell Biochemistry and Gene Regulation, College of Medical Bioengineering and Faculty of Life Sciences, Chongqing University, Shapingba District, Chongqing, China.
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Ren
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D061745:Antioxidant Response Elements; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015870:Gene Expression; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D051266:Nuclear Respiratory Factor 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020033:Protein Isoforms; D016415:Sequence Alignment; D015533:Transcriptional Activation
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D051266:Nuclear Respiratory Factor 1; D020033:Protein Isoforms