19 results on '"Xiao Liu"'
Search Results
2. Natural and synthetic 2-oxoglutarate derivatives are substrates for oncogenic variants of human isocitrate dehydrogenase 1 and 2
- Author
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Xiao Liu, Raphael Reinbold, Shuang Liu, Ryan A. Herold, Patrick Rabe, Stéphanie Duclos, Rahul B. Yadav, Martine I. Abboud, Sandrine Thieffine, Fraser A. Armstrong, Lennart Brewitz, and Christopher J. Schofield
- Subjects
Cell Biology ,Molecular Biology ,Biochemistry - Abstract
Variants of isocitrate dehydrogenase (IDH) 1 and 2 (IDH1/2) alter metabolism in cancer cells by catalyzing the NADPH-dependent reduction of 2-oxoglutate (2OG) to (2R)-hydroxyglutarate (2HG). However, it is unclear how derivatives of 2OG can affect cancer cell metabolism. Here, we used synthetic C3 and C4 alkylated 2OG derivatives to investigate the substrate selectivities of the most common cancer-associated IDH1 variant (R132H IDH1), of two cancer-associated IDH2 variants (R172K IDH2, R140Q IDH2), and of wildtype IDH1/2. Absorbance-based, NMR and electrochemical assays were employed to monitor wildtype IDH1/2 and IDH1/2 variant-catalyzed 2OG derivative turnover in the presence and absence of 2OG. Our results reveal that 2OG derivatives can serve as substrates of the investigated IDH1/2 variants, but not of wildtype IDH1/2, and have the potential to act as 2OG-competitive inhibitors. Kinetic parameters reveal that some 2OG derivatives, including the natural product 3-methyl-2OG, are equally or even more efficient IDH1/2 variant substrates compared to 2OG. Furthermore, NMR and mass spectrometry studies confirmed IDH1/2 variant-catalyzed production of alcohols in the cases of the 3-methyl-, 3-butyl-, and 3-benzyl-substituted 2OG derivatives; a crystal structure of 3-butyl-2OG with an IDH1 variant (R132C/S280F IDH1) reveals active site binding. The combined results highlight the potential for (i) IDH1/2 variant-catalyzed reduction of 2-oxoacids other than 2OG in cells, (ii) modulation of IDH1/2 variant activity by 2-oxoacid natural products, including some present in common foods, (iii) inhibition of IDH1/2 variants via active site binding rather than the established allosteric mode of inhibition, and (iv) possible use of IDH1/2 variants as biocatalysts.
- Published
- 2023
3. Polo-like kinase 1 (PLK1) O-GlcNAcylation is essential for dividing mammalian cells and inhibits uterine carcinoma
- Author
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Sheng Yan, Bin Peng, Shifeng Kan, Guangcan Shao, Zhikai Xiahou, Xiangyan Tang, Yong-Xiang Chen, Meng-Qiu Dong, Xiao Liu, Xingzhi Xu, and Jing Li
- Subjects
Cell Biology ,Molecular Biology ,Biochemistry - Published
- 2023
4. N6-methyladenosine (m6A) RNA methylation mediated by methyltransferase complex subunit WTAP regulates amelogenesis
- Author
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Furong, Xie, Xueqin, Zhu, Xiao, Liu, Hui, Chen, and Jun, Wang
- Subjects
Mammals ,Mice ,Amelogenesis ,Animals ,RNA ,Hedgehog Proteins ,Methyltransferases ,RNA Splicing Factors ,Cell Biology ,Methylation ,Molecular Biology ,Biochemistry - Abstract
N6-methyladenosine (m6A) RNA methylation, one of the most widespread posttranscriptional modifications in eukaryotes, plays crucial roles in various developmental processes. The m6A modification process is catalyzed by a methyltransferase complex that includes Wilms tumor 1-associated protein (WTAP) as a key component. Whether the development of dental enamel is regulated by m6A RNA methylation in mammals remains unclear. Here, we reveal that WTAP is widely expressed from the early stage of tooth development. Specific inactivation of Wtap in mouse enamel epithelium by the Cre/loxp system leads to serious developmental defects in amelogenesis. In Wtap conditional KO mice, we determined that the differentiation of enamel epithelial cells into mature ameloblasts at the early stages of enamel development is affected. Mechanistically, loss of Wtap inhibits the expression of Sonic hedgehog (SHH), which plays an important role in the generation of ameloblasts from stem cells. Together, our findings provide new insights into the functional role of WTAP-mediated m6A methylation in amelogenesis in mammals.
- Published
- 2022
5. Selective PPARδ agonist seladelpar suppresses bile acid synthesis by reducing hepatocyte CYP7A1 via the fibroblast growth factor 21 signaling pathway
- Author
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Tetsuya Kouno, Xiao Liu, Huayi Zhao, Tatiana Kisseleva, Edward E. Cable, and Bernd Schnabl
- Subjects
Bile Acids and Salts ,Fibroblast Growth Factors ,Mice ,Hepatocytes ,Animals ,Humans ,PPAR delta ,Cell Biology ,Acetates ,Cholesterol 7-alpha-Hydroxylase ,Molecular Biology ,Biochemistry ,Signal Transduction - Abstract
Peroxisome proliferator-activated receptor delta (PPARδ) agonists have been shown to exert beneficial effects in liver disease and reduce total bile acid levels. The mechanism(s) whereby PPARδ agonism reduces bile acid levels are, however, unknown, and therefore the aim of the present study was to investigate the molecular pathways responsible for reducing bile acid synthesis in hepatocytes, following treatment with the selective PPARδ agonist, seladelpar. We show that administration of seladelpar to WT mice repressed the liver expression of cholesterol 7 alpha-hydroxylase (Cyp7a1), the rate-limiting enzyme for bile acid synthesis, and decreased plasma 7α-hydroxy-4-cholesten-3-one (C4), a freely diffusible metabolite downstream of Cyp7a1. In primary mouse hepatocytes, seladelpar significantly reduced the expression of Cyp7a1 independent of the nuclear bile acid receptor, Farnesoid X receptor. In addition, seladelpar upregulated fibroblast growth factor 21 (Fgf21) in mouse liver, serum, and in cultured hepatocytes. We demonstrate that recombinant Fgf21 protein activated the c-Jun N-terminal kinase (JNK) signaling pathway and repressed Cyp7a1 gene expression in primary hepatocytes. The suppressive effect of seladelpar on Cyp7a1 expression was blocked by a JNK inhibitor as well as in the absence of Fgf21, indicating that Fgf21 plays an indispensable role in PPARδ-mediated downregulation of Cyp7a1. Finally, reduction of CYP7A1 expression by seladelpar was confirmed in primary human hepatocytes. In conclusion, we show that seladelpar reduces bile acid synthesis via an FGF21-dependent mechanism that signals at least partially through JNK to repress CYP7A1.
- Published
- 2022
6. Mechanisms of phosphatidylserine influence on viral production: A computational model of Ebola virus matrix protein assembly.
- Author
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Xiao Liu, Pappas, Ethan J., Husby, Monica L., Motsa, Balindile B., Stahelin, Robert V., and Pienaar, Elsje
- Subjects
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EXTRACELLULAR matrix proteins , *EBOLA virus , *PHOSPHATIDYLSERINES , *VIRAL proteins , *VIRUS-like particles , *EBOLA virus disease - Abstract
Ebola virus (EBOV) infections continue to pose a global public health threat, with high mortality rates and sporadic outbreaks in Central and Western Africa. A quantitative understanding of the key processes driving EBOV assembly and budding could provide valuable insights to inform drug development. Here, we use a computational model to evaluate EBOV matrix assembly. Our model focuses on the assembly kinetics of VP40, the matrix protein in EBOV, and its interaction with phosphatidylserine (PS) in the host cell membrane. It has been shown that mammalian cells transfected with VP40-expressing plasmids are capable of producing virus-like particles (VLPs) that closely resemble EBOV virions. Previous studies have also shown that PS levels in the host cell membrane affects VP40 association with the plasma membrane inner leaflet and that lower membrane PS levels result in lower VLP production. Our computational findings indicate that PS may also have a direct influence on VP40 VLP assembly and budding, where a higher PS level will result in a higher VLP budding rate and filament dissociation rate. Our results further suggest that the assembly of VP40 filaments follow the nucleation-elongation theory, where initialization and oligomerization of VP40 are two distinct steps in the assembly process. Our findings advance the current understanding of VP40 VLP formation by identifying new possible mechanisms of PS influence on VP40 assembly. We propose that these mechanisms could inform treatment strategies targeting PS alone or in combination with other VP40 assembly steps. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
7. Suppression of WHITE COLLAR-independent frequency Transcription by Histone H3 Lysine 36 Methyltransferase SET-2 Is Necessary for Clock Function in Neurospora
- Author
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Kexin Gai, Zhipeng Zhou, Farah Naz Kaleri, Xiao Liu, Joonseok Cha, Qingqing Liu, Guangyan Sun, Qun He, and Ying Wang
- Subjects
0301 basic medicine ,Methyltransferase ,Genes, Fungal ,Circadian clock ,Biochemistry ,Histone Deacetylases ,Fungal Proteins ,Gene Knockout Techniques ,03 medical and health sciences ,Histone H3 ,0302 clinical medicine ,Circadian Clocks ,Gene Expression Regulation, Fungal ,Gene Regulation ,Molecular Biology ,Genetics ,Neurospora crassa ,biology ,Histone-Lysine N-Methyltransferase ,Cell Biology ,Recombinant Proteins ,Chromatin ,DNA-Binding Proteins ,CLOCK ,030104 developmental biology ,Histone ,Acetylation ,Mutagenesis, Site-Directed ,biology.protein ,Mutant Proteins ,Histone deacetylase ,030217 neurology & neurosurgery ,Transcription Factors - Abstract
The circadian system in Neurospora is based on the transcriptional/translational feedback loops and rhythmic frequency (frq) transcription requires the WHITE COLLAR (WC) complex. Our previous paper has shown that frq could be transcribed in a WC-independent pathway in a strain lacking the histone H3K36 methyltransferase, SET-2 (su(var)3-9-enhancer-of-zeste-trithorax-2) (1), but the mechanism was unclear. Here we disclose that loss of histone H3K36 methylation, due to either deletion of SET-2 or H3K36R mutation, results in arrhythmic frq transcription and loss of overt rhythmicity. Histone acetylation at frq locus increases in set-2 KO mutant. Consistent with these results, loss of H3K36 methylation readers, histone deacetylase RPD-3 (reduced potassium dependency 3) or EAF-3 (essential SAS-related acetyltransferase-associated factor 3), also leads to hyperacetylation of histone at frq locus and WC-independent frq expression, suggesting that proper chromatin modification at frq locus is required for circadian clock operation. Furthermore, a mutant strain with three amino acid substitutions (histone H3 lysine 9, 14, and 18 to glutamine) was generated to mimic the strain with hyperacetylation state of histone H3. H3K9QK14QK18Q mutant exhibits the same defective clock phenotype as rpd-3KO mutant. Our results support a scenario in which H3K36 methylation is required to establish a permissive chromatin state for circadian frq transcription by maintaining proper acetylation status at frq locus.
- Published
- 2016
8. Phosphorylation of Tyrosine 1070 at the GluN2B Subunit Is Regulated by Synaptic Activity and Critical for Surface Expression of N-Methyl-d-aspartate (NMDA) Receptors
- Author
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Jianhong Luo, Xun-yi Yan, Lin Peng, Qian Yang, Heng Ai, Wei Yang, Weiqing Fang, Jie-jie Wang, Wen Lu, Bin Zhang, Xiao Liu, and Jian Li
- Subjects
inorganic chemicals ,endocrine system diseases ,Biology ,Proto-Oncogene Proteins c-fyn ,Receptors, N-Methyl-D-Aspartate ,environment and public health ,Biochemistry ,Rats, Sprague-Dawley ,Mice ,chemistry.chemical_compound ,FYN ,Neurobiology ,Animals ,Phosphorylation ,Tyrosine ,Molecular Biology ,Mice, Knockout ,Neuronal Plasticity ,Kinase ,nutritional and metabolic diseases ,Tyrosine phosphorylation ,Cell Biology ,Rats ,Cell biology ,enzymes and coenzymes (carbohydrates) ,nervous system ,Gene Expression Regulation ,chemistry ,Synapses ,Synaptic plasticity ,NMDA receptor ,hormones, hormone substitutes, and hormone antagonists ,Proto-oncogene tyrosine-protein kinase Src - Abstract
The number and subunit composition of synaptic N-methyl-d-aspartate receptors (NMDARs) play critical roles in synaptic plasticity, learning, and memory and are implicated in neurological disorders. Tyrosine phosphorylation provides a powerful means of regulating NMDAR function, but the underling mechanism remains elusive. In this study we identified a tyrosine site on the GluN2B subunit, Tyr-1070, which was phosphorylated by a proto-oncogene tyrosine-protein (Fyn) kinase and critical for the surface expression of GluN2B-containing NMDARs. The phosphorylation of GluN2B at Tyr-1070 was required for binding of Fyn kinase to GluN2B, which up-regulated the phosphorylation of GluN2B at Tyr-1472. Moreover, our results revealed that the phosphorylation change of GluN2B at Tyr-1070 accompanied the Tyr-1472 phosphorylation and Fyn associated with GluN2B in synaptic plasticity induced by both chemical and contextual fear learning. Taken together, our findings provide a new mechanism for regulating the surface expression of NMDARs with implications for synaptic plasticity.
- Published
- 2015
9. Molecular Characterization and Phylogenetic Analysis of Two Novel Regio-specific Flavonoid Prenyltransferases from Morus alba and Cudrania tricuspidata
- Author
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Dan Xie, Lin Yang, Ruishan Wang, Ridao Chen, Xiao Liu, Dawei Chen, Kebo Xie, Xiaoyu Tao, Jianhua Li, Yunze Yin, Jungui Dai, and Jian-Hua Zou
- Subjects
Stereochemistry ,Molecular Sequence Data ,Flavonoid ,Plant Biology ,Moraceae ,Biochemistry ,Flavones ,Homology (biology) ,Substrate Specificity ,chemistry.chemical_compound ,Prenylation ,Phylogenetics ,Amino Acid Sequence ,Cloning, Molecular ,Molecular Biology ,Conserved Sequence ,Phylogeny ,Plant Proteins ,Homogentisate 1,2-dioxygenase ,Flavonoids ,chemistry.chemical_classification ,Alkyl and Aryl Transferases ,biology ,Cell Biology ,biology.organism_classification ,chemistry ,Morus ,Isoliquiritigenin - Abstract
Prenylated flavonoids are attractive specialized metabolites with a wide range of biological activities and are distributed in several plant families. The prenylation catalyzed by prenyltransferases represents a Friedel-Crafts alkylation of the flavonoid skeleton in the biosynthesis of natural prenylated flavonoids and contributes to the structural diversity and biological activities of these compounds. To date, all identified plant flavonoid prenyltransferases (FPTs) have been identified in Leguminosae. In the present study two new FPTs, Morus alba isoliquiritigenin 3'-dimethylallyltransferase (MaIDT) and Cudrania tricuspidata isoliquiritigenin 3'-dimethylallyltransferase (CtIDT), were identified from moraceous plants M. alba and C. tricuspidata, respectively. MaIDT and CtIDT shared low levels of homology with the leguminous FPTs. MaIDT and CtIDT are predicted to be membrane-bound proteins with predicted transit peptides, seven transmembrane regions, and conserved functional domains that are similar to other homogentisate prenyltransferases. Recombinant MaIDT and CtIDT were able to regioselectively introduce dimethylallyl diphosphate into the A ring of three flavonoids with different skeleton types (chalcones, isoflavones, and flavones). Phylogenetic analysis revealed that MaIDT and CtIDT are distantly related to their homologs in Leguminosae, which suggests that FPTs in Moraceae and Leguminosae might have evolved independently. MaIDT and CtIDT represent the first two non-Leguminosae FPTs to be identified in plants and could thus lead to the identification of additional evolutionarily varied FPTs in other non-Leguminosae plants and could elucidate the biosyntheses of prenylated flavonoids in various plants. Furthermore, MaIDT and CtIDT might be used for regiospecific prenylation of flavonoids to produce bioactive compounds for potential therapeutic applications due to their high efficiency and catalytic promiscuity.
- Published
- 2014
10. Functional Identification of a Hydroxyproline-O-galactosyltransferase Specific for Arabinogalactan Protein Biosynthesis in Arabidopsis
- Author
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Allan M. Showalter, Klaus Himmeldirk, Ahmed Faik, Marcia J. Kieliszewski, Xiao Liu, Michael A. Held, Yan Liang, and Debarati Basu
- Subjects
animal structures ,Glycosylation ,Immunoblotting ,Arabidopsis ,Molecular Conformation ,Plant Biology ,macromolecular substances ,Galactans ,Biochemistry ,Catalysis ,Gene Expression Regulation, Enzymologic ,Pichia ,Substrate Specificity ,Pichia pastoris ,chemistry.chemical_compound ,Cell Wall ,Gene Expression Regulation, Plant ,Arabinogalactan ,Microsomes ,Glycosyltransferase ,Cloning, Molecular ,Molecular Biology ,Arabinogalactan protein ,Galactosyltransferase ,Microscopy, Confocal ,biology ,Arabidopsis Proteins ,food and beverages ,Cell Biology ,Chromatography, Ion Exchange ,Galactosyltransferases ,biology.organism_classification ,Molecular biology ,carbohydrates (lipids) ,Plant Leaves ,Hydroxyproline ,chemistry ,Galactose ,Mutation ,biology.protein ,lipids (amino acids, peptides, and proteins) - Abstract
Although plants contain substantial amounts of arabinogalactan proteins (AGPs), the enzymes responsible for AGP glycosylation are largely unknown. Bioinformatics indicated that AGP galactosyltransferases (GALTs) are members of the carbohydrate-active enzyme glycosyltransferase (GT) 31 family (CAZy GT31) involved in N- and O-glycosylation. Six Arabidopsis GT31 members were expressed in Pichia pastoris and tested for enzyme activity. The At4g21060 gene (named AtGALT2) was found to encode activity for adding galactose (Gal) to hydroxyproline (Hyp) in AGP protein backbones. AtGALT2 specifically catalyzed incorporation of [(14)C]Gal from UDP-[(14)C]Gal to Hyp of model substrate acceptors having AGP peptide sequences, consisting of non-contiguous Hyp residues, such as (Ala-Hyp) repetitive units exemplified by chemically synthesized (AO)7 and anhydrous hydrogen fluoride-deglycosylated d(AO)51. Microsomal preparations from Pichia cells expressing AtGALT2 incorporated [(14)C]Gal to (AO)7, and the resulting product co-eluted with (AO)7 by reverse-phase HPLC. Acid hydrolysis of the [(14)C]Gal-(AO)7 product released (14)C-radiolabel as Gal only. Base hydrolysis of the [(14)C]Gal-(AO)7 product released a (14)C-radiolabeled fragment that co-eluted with a Hyp-Gal standard after high performance anion-exchange chromatography fractionation. AtGALT2 is specific for AGPs because substrates lacking AGP peptide sequences did not act as acceptors. Moreover, AtGALT2 uses only UDP-Gal as the substrate donor and requires Mg(2+) or Mn(2+) for high activity. Additional support that AtGALT2 encodes an AGP GALT was provided by two allelic AtGALT2 knock-out mutants, which demonstrated lower GALT activities and reductions in β-Yariv-precipitated AGPs compared with wild type plants. Confocal microscopic analysis of fluorescently tagged AtGALT2 in tobacco epidermal cells indicated that AtGALT2 is probably localized in the endomembrane system consistent with its function.
- Published
- 2013
11. Coordinated Regulation of Transcription Factor Bcl11b Activity in Thymocytes by the Mitogen-activated Protein Kinase (MAPK) Pathways and Protein Sumoylation
- Author
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Ling-juan Zhang, Walter K. Vogel, Xiao Liu, Acharawan Topark-Ngarm, Brian Arbogast, Mark Leid, Theresa M. Filtz, and Claudia S. Maier
- Subjects
Protein sumoylation ,MAPK/ERK pathway ,MAP Kinase Signaling System ,Molecular Sequence Data ,SUMO protein ,Thymus Gland ,Biology ,Biochemistry ,Mass Spectrometry ,Cell Line ,Mice ,Transcriptional regulation ,Animals ,Humans ,Gene Regulation ,Amino Acid Sequence ,Phosphorylation ,Molecular Biology ,Transcription factor ,Calcimycin ,Cells, Cultured ,Histone Acetyltransferase p300 ,Sequence Homology, Amino Acid ,Tumor Suppressor Proteins ,Sumoylation ,Cell Biology ,Molecular biology ,Cell biology ,Repressor Proteins ,Signal transduction - Abstract
The transcriptional regulatory protein Bcl11b is essential for T-cell development. We have discovered a dynamic, MAPK-regulated pathway involving sequential, linked, and reversible post-translational modifications of Bcl11b in thymocytes. MAPK-mediated phosphorylation of Bcl11b was coupled to its rapid desumoylation, which was followed by a subsequent cycle of dephosphorylation and resumoylation. Additionally and notably, we report the first instance of direct identification by mass spectrometry of a site of small ubiquitin-like modifier (SUMO) adduction, Lys-679 of Bcl11b, in a protein isolated from a native, mammalian cell. Sumoylation of Bcl11b resulted in recruitment of the transcriptional co-activator p300 to a Bcl11b-repressed promoter with subsequent induction of transcription. Prolonged treatment of native thymocytes with phorbol 12,13-dibutyrate together with the calcium ionophore A23187 also promoted ubiquitination and proteasomal degradation of Bcl11b, providing a mechanism for signal termination. A Bcl11b phospho-deSUMO switch was identified, the basis of which was phosphorylation-dependent recruitment of the SUMO hydrolase SENP1 to phospho-Bcl11b, coupled to hydrolysis of SUMO-Bcl11b. These results define a regulatory pathway in thymocytes that includes the MAPK pathways and upstream signaling components, Bcl11b and the associated nucleosome remodeling and deacetylation (NuRD) complex, SENP proteins, the Bcl11b protein phosphatase 6, the sumoylation machinery, the histone acetyltransferase p300, and downstream transcriptional machinery. This pathway appears to facilitate derepression of repressed Bcl11b target genes as immature thymocytes initiate differentiation programs, biochemically linking MAPK signaling with the latter stages of T-cell development.
- Published
- 2012
12. A Chicken Ovalbumin Upstream Promoter Transcription Factor I (COUP-TFI) Complex Represses Expression of the Gene Encoding Tumor Necrosis Factor α-induced Protein 8 (TNFAIP8)
- Author
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Mark Leid, Ling-juan Zhang, Philip R. Gafken, Chrissa Kioussi, and Xiao Liu
- Subjects
Chicken ovalbumin upstream promoter-transcription factor ,Biology ,Biochemistry ,Inhibitor of Apoptosis Proteins ,Sp3 transcription factor ,Humans ,Transcription, Chromatin, and Epigenetics ,Promoter Regions, Genetic ,Molecular Biology ,Sp1 transcription factor ,COUP Transcription Factor I ,Tumor Necrosis Factor-alpha ,Proteins ,Cell Biology ,COUP-TFI ,TCF4 ,Molecular biology ,Repressor Proteins ,Gene Expression Regulation ,Nuclear receptor ,Multiprotein Complexes ,Apoptosis Regulatory Proteins ,Corepressor ,HeLa Cells ,Signal Transduction - Abstract
The orphan nuclear receptor chicken ovalbumin upstream promoter transcription factor I (COUP-TFI) plays key roles in development and homeostasis. A tandem affinity purification procedure revealed that COUP-TFI associated with a number of transcriptional regulatory proteins in HeLa S3 cells, including the nuclear receptor corepressor (NCoR), TIF1beta/KAP-1, HDAC1, and the SWI/SNF family member Brahma. The proapoptotic protein DBC1 was also identified in COUP-TFI complexes. In vitro experiments revealed that COUP-TFI interacted directly with NCoR but in a manner different from that of other nuclear receptors. DBC1 stabilized the interaction between COUP-TFI and NCoR by interacting directly with both proteins. The gene encoding the anti-apoptotic protein TNFAIP8 (tumor necrosis factor alpha (TNFalpha)-induced protein 8) was identified as being repressed by COUP-TFI in a manner that required several of the component proteins of the COUP-TFI complex. Finally, our studies highlight a central role for COUP-TFI in the induction of the TNFAIP8 promoter by TNFalpha. Together, these studies identify a novel COUP-TFI complex that functions as a repressor of transcription and may play a role in the TNFalpha signaling pathways.
- Published
- 2009
13. Ankyrin B Modulates the Function of Na,K-ATPase/lnositol 1,4,5-Trisphosphate Receptor Signaling Microdomain.
- Author
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Xiao Liu, Špicarová, Zuzana, Rydholm, Susanna, Li, Juan, Brjsmar, Hjalmar, and Aperia, Anita
- Subjects
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BIOCHEMISTRY , *CELL membranes , *CELL culture , *OSCILLATIONS , *CALCIUM , *ADENOSINE triphosphatase - Abstract
Na,K-ATPase and inositol 1,4,5-trisphosphate (1P3) receptor (IP3R) can form a signaling microdomain that in the presence of ouabain triggers highly regular calcium oscillations. Down- stream effects include NF-KB activation. Here we report that ankyrin B (Ank-B), expressed in most mammalian cells, plays a pivotal role in the function of the Na,K-ATPase/IP3R signaling microdomain. In studies performed on a monkey kidney cell line, we show that Ank-B co-precipitates with both Na,K- ATPase and IP3R. We identify the N terminus tail of the Na,K- ATPase catalytic subunit and the N-terminal portion 1-604 of the IP3R as novel binding sites for Ank-B. Knockdown of Ank-B with small interfering RNA reduced the expression of Ank-B to 15-30%. This down-regulation of Ank-B attenuated the inter- action between Na,K-ATPase and IP3R, reduced the number of cells responding to ~M doses of ouabain with calcium oscillations, altered the calcium oscillatory pattern, and abolished the ouabain effect on NF-KB. In contrast, Ank-B down-regulation had no effect on the ion transporting function of Na,K-ATPase and no effect on the distribution and apparent mobility of Na,K- ATPase in the plasma membrane. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
14. Suppression of WHITE COLLAR-independent frequency Transcription by Histone H3 Lysine 36 Methyltransferase SET-2 Is Necessary for Clock Function in Neurospora.
- Author
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Guangyan Sun, Zhipeng Zhou, Xiao Liu, Kexin Gai, Qingqing Liu, Joonseok Cha, Kaleri, Farah Naz, Ying Wang, and Qun He
- Subjects
- *
GENETIC transcription , *HISTONES , *LYSINE , *METHYLTRANSFERASES , *NEUROSPORA , *CIRCADIAN rhythms , *FUNGI - Abstract
The circadian system in Neurospora is based on the transcriptional/translational feedback loops and rhythmic frequency (frq) transcription requires the WHITE COLLAR (WC) complex. Our previous paper has shown that frq could be transcribed in a WC-independent pathway in a strain lacking the histone H3K36 methyltransferase, SET-2 (su(var)3-9-enhancer-of-zestetrithorax-2) (1), but the mechanism was unclear. Here we disclose that loss of histone H3K36 methylation, due to either deletion of SET-2orH3K36Rmutation, results in arrhythmic frq transcription and loss of overt rhythmicity. Histone acetylation at frq locus increases in set-2KO mutant. Consistent with these results, loss of H3K36 methylation readers, histone deacetylase RPD-3 (reduced potassium dependence 3) or EAF-3 (essential SAS-related acetyltransferase-associated factor 3), also leads to hyperacetylation of histone at frq locus and WC-independent frq expression, suggesting that proper chromatin modification at frq locus is required for circadian clock operation. Furthermore, a mutant strain with three amino acid substitutions (histone H3 lysine 9, 14, and 18 to glutamine) was generated to mimic the strain with hyperacetylation state of histone H3. H3K9QK14QK18Q mutant exhibits the same defective clock phenotype as rpd-3KO mutant. Our results support a scenario in which H3K36 methylation is required to establish a permissive chromatin state for circadian frq transcription by maintaining proper acetylation status at frq locus. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
15. Functional Identification of a Hydroxyproline-O-galactosyltransferase Specific for Arabinogalactan Protein Biosynthesis in Arabidopsis.
- Author
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Basu, Debarati, Yan Liang, Xiao Liu, Himmeldirk, Klaus, Faik, Ahmed, Kieliszewski, Marcia, Held, Michael, and Showalter, Allan M.
- Subjects
- *
ARABINOGALACTAN , *GLYCOSYLATION , *GALACTOSYLTRANSFERASES , *ESTERIFICATION , *ARABIDOPSIS , *HYDROLYSIS - Abstract
Although plants contain substantial amounts of arabinogalactan proteins (AGPs), the enzymes responsible for AGP glycosylation are largely unknown. Bioinformatics indicated that AGP galactosyltransferases (GALTs) are members of the carbohydrate-active enzyme glycosyltransferase (GT) 31 family (CAZy GT31) involved in N- and O-glycosylation. Six Arabidopsis GT31 members were expressed in Pichia pastoris and tested for enzyme activity. The At4g21060 gene (named AtGALT2) was found to encode activity for adding galactose (Gal) to hydroxyproline (Hyp) in AGP protein backbones. AtGALT2 specifically catalyzed incorporation of [14C]Gal from UDP-[14C]Gal to Hyp of model substrate acceptors having AGP peptide sequences, consisting of non-contiguous Hyp residues, such as (Ala-Hyp) repetitive units exemplified by chemically synthesized (AO)7 and anhydrous hydrogen fluoride-deglycosylated d(AO)51. Microsomal preparations from Pichia cells expressing AtGALT2 incorporated [14C]Gal to (AO)7, and the resulting product co-eluted with (AO)7 by reverse-phase HPLC. Acid hydrolysis of the [14C]Gal-(AO)7 product released 14C-radiolabel as Gal only. Base hydrolysis of the [14C]Gal-(AO)7 product released a 14C-radiolabeled fragment that co-eluted with a Hyp-Gal standard after high performance anion-exchange chromatography fractionation. AtGALT2 is specific for AGPs because substrates lacking AGP peptide sequences did not act as acceptors. Moreover, AtGALT2 uses only UDP-Gal as the substrate donor and requires Mg2+ or Mn2+ for high activity. Additional support that AtGALT2 encodes an AGP GALT was provided by two allelic AtGALT2 knock-out mutants, which demonstrated lower GALT activities and reductions in β-Yariv-precipitated AGPs compared with wild type plants. Confocal microscopic analysis of fluorescently tagged AtGALT2 in tobacco epidermal cells indicated that AtGALT2 is probably localized in the endomembrane system consistent with its function. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
16. Degradation of the Separase-cleaved Rec8, a Meiotic Cohesin Subunit, by the N-end Rule Pathway.
- Author
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Yu-Jiao Liu, Chao Liu, ZeNan Chang, Wadas, Brandon, Brower, Christopher S., Zhen-Hua Song, Zhi-Liang Xu, Yong-Liang Shang, Wei-Xiao Liu, Li-Na Wang, Wen Dong, Varshavsky, Alexander, Rong-Gui Hu, and Wei Li
- Subjects
- *
COHESINS , *PROTEASOME inhibitors , *UBIQUITIN ligases , *SACCHAROMYCES cerevisiae , *APOPTOTIC bodies , *PHYSIOLOGY - Abstract
The Ate1 arginyltransferase (R transferase) is a component of the N-end rule pathway, which recognizes proteins containing N-terminal degradation signals called N-degrons, polyubiquitylates these proteins and thereby causes their degradation by the proteasome. Ate1 arginylates N-terminal Asp, Glu or (oxidized) Cys. The resulting N-terminal Arg is recognized by ubiquitin ligases of the N-end rule pathway. In the yeast Saccharomyces cerevisiae, the separase-mediated cleavage of the Scc1/Rad21/Mcd1 cohesin subunit generates a C-terminal fragment that bears N terminal Arg and is destroyed by the N-end end rule pathway without requirement for arginylation. In contrast, the separase-mediated cleavage of Rec8, the mammalian meiotic cohesin subunit, yields a fragment bearing N terminal Glu, a substrate of the Ate1 R transferase. Here we constructed and used a germ cells confined Ate1-/- mouse strain to analyze the separase-generated C-terminal fragment of Rec8. We show that this fragment is a short-lived N-end rule substrate, that its degradation requires N terminal arginylation, and that male Ate1-/- mice are nearly infertile, owing to massive apoptotic death of Ate1-/- spermatocytes during the metaphase of meiosis I. These effects of Ate1 ablation are inferred to be caused, at least in part, by the failure to destroy the C-terminal fragment of Rec8 in the absence of N-terminal arginylation. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
17. Phosphorylation of Tyrosine 1070 at the GluN2B Subunit Is Regulated by Synaptic Activity and Critical for Surface Expression of N-Methyl-D-aspartate (NMDA) Receptors.
- Author
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Wen Lu, Weiqing Fang, Jian Li, Bin Zhang, Qian Yang, Xunyi Yan, Lin Peng, Heng Ai, Jie-jie Wang, Xiao Liu, Jianhong Luo, and Wei Yang
- Subjects
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TYROSINE metabolism , *PHOSPHORYLATION , *CHEMICAL kinetics , *TYROSINOSIS , *METABOLIC disorders , *PHYSIOLOGY - Abstract
The number and subunit composition of synaptic N-methyl- D-aspartate receptors (NMDARs) play critical roles in synaptic plasticity, learning, and memory and are implicated in neurological disorders. Tyrosine phosphorylation provides a powerful means of regulatingNMDARfunction, but the underling mechanism remains elusive. In this study we identified a tyrosine site on the GluN2B subunit, Tyr-1070, which was phosphorylated by a proto-oncogene tyrosine-protein (Fyn) kinase and critical for the surface expression of GluN2B-containing NMDARs. The phosphorylation of GluN2B at Tyr-1070 was required for binding of Fyn kinase to GluN2B, which up-regulated the phosphorylation of GluN2B at Tyr-1472. Moreover, our results revealed that the phosphorylation change of GluN2B at Tyr-1070 accompanied the Tyr-1472 phosphorylation and Fyn associated with GluN2B in synaptic plasticity induced by both chemical and contextual fear learning. Taken together, our findings provide a new mechanism for regulating the surface expression of NMDARs with implications for synaptic plasticity. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
18. Molecular Characterization and Phylogenetic Analysis of Two Novel Regio-specific Flavonoid Prenyltransferases from Morus alba and Cudrania tricuspidata.
- Author
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Ruishan Wang, Ridao Chen, Jianhua Li, Xiao Liu, Kebo Xie, Dawei Chen, Yunze Yin, Xiaoyu Tao, Dan Xie, Jianhua Zou, Lin Yang, and Jungui Dai
- Subjects
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FLAVONOIDS , *PHYLOGENY , *WHITE mulberry , *LEGUMES , *BIOSYNTHESIS - Abstract
Prenylated flavonoids are attractive specialized metabolites with a wide range of biological activities and are distributed in several plant families. The prenylation catalyzed by prenyltransferases represents a Friedel-Crafts alkylation of the flavonoid skeleton in the biosynthesis of natural prenylated flavonoids and contributes to the structural diversity and biological activities of these compounds. To date, all identified plant flavonoid prenyltransferases (FPTs) have been identified in Leguminosae. In the present study two new FPTs, Morus alba isoliquiritigenin 3'-dimethylallyltransferase (MaIDT) and Cudrania tricuspidata isoliquiritigenin 3'-dimethylallyltransferase (CtIDT), were identified from moraceous plants M. alba and C. tricuspidata, respectively. MaIDT and CtIDT shared low levels of homology with the leguminous FPTs. MaIDT and CtIDT are predicted to be membrane-bound proteins with predicted transit peptides, seven transmembrane regions, and conserved functional domains that are similar to other homogentisate prenyltransferases. Recombinant MaIDT and CtIDT were able to regioselectively introduce dimethylallyl diphosphate into the A ring of three flavonoids with different skeleton types (chalcones, isoflavones, and flavones). Phylogenetic analysis revealed thatMaIDT and CtIDT are distantly related to their homologs in Leguminosae, which suggests that FPTs in Moraceae and Leguminosae might have evolved independently. MaIDT and CtIDT represent the first two non-Leguminosae FPTs to be identified in plants and could thus lead to the identification of additional evolutionarily varied FPTs in other non-Leguminosae plants and could elucidate the biosyntheses of prenylated flavonoids in various plants. Furthermore, MaIDT and CtIDT might be used for regiospecific prenylation of flavonoids to produce bioactive compounds for potential therapeutic applications due to their high efficiency and catalytic promiscuity. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
19. BmCREC Is an Endoplasmic Reticulum(ER) Resident Protein and Required for ER/Golgi Morphology.
- Author
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Qiao Wang, Birong Shen, Pengli Zheng, Hui Feng, Yige Guo, Wenyuan Cao, Liang Chen, Xiao Liu, Guodong Zhao, Sizheng Xu, Weide Shen, Jianguo Chen, and Junlin Teng
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SILKWORMS , *INTRACELLULAR membranes , *ENDOPLASMIC reticulum , *GOLGI apparatus , *DNA supercoiling - Abstract
Silkworm posterior silkgland is a model for studying intracellular trafficking. Here, using this model, we identify several potential cargo proteins of BmKinesin-1 and focus on one candidate, BmCREC. BmCREC (also known as Bombyx mori DNA supercoiling factor, BmSCF) was previously proposed to supercoil DNA in the nucleus. However, we show here that BmCREC is localized in the ER lumen. Its C-terminal tetrapeptide HDEF is recognized by the KDEL receptor, and subsequently it is retrogradely transported by coat protein I (COPI) vesicles to the ER. Lacking the HDEF tetrapeptide of BmCREC or knocking down COPI subunits results in decreased ER retention and simultaneously increased secretion of BmCREC. Furthermore, we find that BmCREC knock-down markedly disrupts themorphology of the ER and Golgi apparatus and leads to a defect of posterior silkgland tube expansion. Together, our results clarify the ER retention mechanism of BmCREC and reveal that BmCREC is indispensable for maintaining ER/Golgi morphology. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
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