中国人群中抗结核药物引发肝损伤的易感基因标记研究

为系统性研究中国人群中抗结核药物引发肝损伤的易感基因标记,本研究以41例抗结核药物引发肝损伤的病人和39例健康对照为研究对象,采用Haloplex捕获测序的方法对其基因组中药物代谢、转运和免疫相关通路的109个基因进行靶向测序。用Plink软件对DNA突变位点与肝损伤的发生进行关联分析,以千人基因组计划东亚人群作为对照组,对显著性位点进行验证,并用SIFT和Polyphen2软件对预测显著关联的位点进行功能预测。结果发现UGT1A4 rs2011404(X^2=4.6809,P=0.0305)是抗结核药物引发的肝损伤的易感基因标记,且rs2011404突变可能引起UGT1A4蛋白的功能障碍。本研究为临床上对抗结核药物的合理用药提供了有益的参考。     

Phenylalanine 93 of the human UGT1A10 plays a major role in the interactions of the enzyme with estrogens

Little is currently known about the substrate binding site of the human UDP-glucuronosyltransferases (UGTs) and the structural elements that affect their complex substrate selectivity. In order to further understand and extend our earlier findings with phenylalanines 90 and 93 of UGT1A10, we have replaced each of them with Gly, Ala, Val, Leu, Ile or Tyr, and tested the activity of the resulting 12 mutants toward eight different substrates. Apart from scopoletin glucuronidation, the F90 mutants other than F90L were nearly inactive, while the F93 mutants’ activity was strongly substrate dependent. Hence, F93L displayed high entacapone and 1-naphthol glucuronidation rates, whereas F93G, which was nearly inactive in entacapone glucuronidation, was highly active toward estradiol, estriol and even ethinylestradiol, a synthetic estrogen that is a poor substrate for the wild-type UGT1A10. Kinetic analyses of 4-nitrophenol, estradiol and ethinylestradiol glucuronidation by the mutants that catalyzed the respective reactions at considerable rates, revealed increased K_m values for 4-nitrophenol and estradiol in all the mutants, whilst the K_m values of F93G and F93A for ethinylestradiol were lower than in control UGT1A10. Based on the activity results and a new molecular model of UGT1A10, it is suggested that both F90 and F93 are located in a surface helix at the far end of the substrate binding site. Nevertheless, only F93 directly affects the selectivity of UGT1A10 toward large and rigid estrogens, particularly those with substitutions at the D ring. The effects of F93 mutations on the glucuronidation of smaller or less rigid substrates are indirect, however.     

N9-substituted derivatives of kinetin: effective anti-senescence agents

The first isolated cytokinin, 6-furfurylaminopurine (kinetin or Kin), was identified almost 55 years ago. Its biological effects on plant cells and tissues include influences on such processes as gene expression, cell cycle, chloroplast development, chlorophyll biosynthesis, stimulation of vascular development, delay of senescence, and mobilization of nutrients. In the present study we prepared a series of eight N9-substituted Kin derivatives, and characterized them with available physicochemical methods such as CI+ mass spectrometry and ¹H NMR spectroscopy. All compounds were tested in three classical cytokinin bioassays: a tobacco callus assay, an Amaranthus assay, and a senescence assay with excised wheat leaves. The ability of the compounds to interact with Arabidopsis cytokinin receptors CRE1/AHK4 and AHK3 was tested in a bacterial receptor assay. Prepared derivatives with certain substitutions of the N9-atom of the purine moiety enhanced the cytokinin activity of the parent compound in the bioassays to a remarkable degree but negatively affected its perception by CRE1/AHK4 and AHK3. The ability of compounds to delay the senescence of excised wheat leaves in both dark and light conditions, was highly correlated with their ability to influence membrane lipid peroxidation, which is a typical symptom of senescence. Our results were corroborated by gene expression profiling of those genes involved in cytokinin metabolism and perception, plant senescence, and the stress response, and suggest that prepared kinetin derivatives might be used as potent anti-senescence agents.     

Structure and action of the C-C bond-forming glycosyltransferase UrdGT2 involved in the biosynthesis of the antibiotic urdamycin

The glycosyltransferase UrdGT2 from Streptomyces fradiae catalyzes the formation of a glycosidic C-C bond between a polyketide aglycone and D-olivose. The enyzme was expressed in Escherichia coli, purified and crystallized. Its structure was established by X-ray diffraction at 1.9 A resolution. It is the first structure of a C-glycosyltransferase. UrdGT2 belongs to the structural family GT-B of the glycosyltransferases and is likely to form a C(2)-symmetric dimer in solution. The binding structures of donor and acceptor substrates in five structurally homologous enzymes provided a clear and consistent guide for the substrate-binding structure in UrdGT2. The modeled substrate locations suggest the deeply buried Asp137 as the activator for C-C bond formation and explain the reaction. The putative model can be used to design mutations that change the substrate specificity. Such mutants are of great interest in overcoming the increasing danger of antibiotic resistance.     

Phenylalanine(90) and phenylalanine(93) are crucial amino acids within the estrogen binding site of the human UDP-glucuronosyltransferase 1A10

Human UDP-glucuronosyltransferase 1A10 has been identified as the major isoform involved in the biotransformation of a wide range of phenolic substrates, including native estrogens and their oxidized metabolites. Our recent studies point to the F(90)-M(91)-V(92)-F(93) amino acid motif of UGT1A10, which was identified using photoaffinity labeling followed by LC-MS/MS analysis, as a key determinant of the binding of phenolic substrates. In this report, we have evaluated the role of F(90), V(92), and F(93) in the recognition of estrogens by UGT1A10 using site-directed mutagenesis. Kinetic studies using five mutants revealed that F(90) and F(93) are critical residues for the recognition of all estrogen substrates. The substitution of F(90) with alanine totally abolished the activity of this enzyme toward all the estrogens investigated. Overall, sequential removal for the aromatic ring (F to L) and of the hydrophobic chain (F to A and V to A) from amino acids 90, 92, and 93 effectively alters estrogen recognition. This demonstrates that individual features of the native and hydroxylated estrogens determine the specific binding properties of the compound within the binding site of the human UGT1A10 and the mutants. The resulting activities are completely abolished, unchanged, increased, or decreased depending on the structures of both the mutant and the substrate. The novel identification of UGT1A10 as the major isoform involved in the glucuronidation of all estrogens and the discovery of the importance of the FMVF motif in the binding of steroids will help to elucidate the molecular mechanism of glucuronidation, resulting in the design of more effective estrogen-based therapies.     

Eudismic analysis of tricyclic sesquiterpenoid alcohols: lead structures for the design of potent inhibitors of the human UDP-glucuronosyltransferase 2B7

The epimeric tricyclic sesquiterpenoid alcohols globulol, epiglobulol, cedrol, epicedrol, longifolol, and isolongifolol were investigated in their ability to inhibit the recombinant human UDP-glucuronosyltransferase (UGT) 2B7. The stereoisomers displayed rapidly reversible competitive inhibition, which was substrate-independent. Longifolol and its stereoisomer isolongifolol displayed the lowest competitive inhibition constants (K(ic)) of 23 and 26 nM, respectively. The K(ic) values of cedrol and its epimer epicedrol were 0.15 and 0.21 microM, those of globulol and epiglobulol were 5.4 and 4.0 microM, respectively. The diastereomeric alcohols exhibited nearly identical affinities toward UGT2B7 indicating that the spatial arrangement of the hydroxy group had no influence on the dissociation of the enzyme-terpenoid complex. The high affinities stemmed presumably from mere hydrophobic interactions between the hydrocarbon scaffold of the terpenoid alcohol and the binding site of the enzyme. Glucuronidation assays revealed that there were large differences in the rates at which the epimeric alcohols were conjugated. Therefore, the spatial arrangement of the hydroxy group controlled the rate of the UGT2B7-catalyzed reaction. The introduction of a methyl group into the side chain of isolongifolol and longifolol increased the steric hindrance. As a result, the rate of the UGT2B7-catalyzed reaction was decreased by more than 88%. The findings indicated that the rate of the UGT2B7-catalyzed glucuronidation is significantly controlled by stereochemical and steric factors. Considering the high inhibition levels exerted by the tricyclic sesquiterpenoid alcohols, these compounds might serve as valuable lead structures for the design of potent inhibitors for UGT2B7.     

布渣叶糖基转移酶MpUGT1基因cDNA克隆及生物信息学和表达分析

UGT催化的糖基转移反应对合成黄酮苷类至关重要。为探究影响布渣叶黄酮苷生物合成的糖基转移酶,本研究参考布渣叶转录组数据,设计特异性引物,采用RT-PCR法对布渣叶中的UDP-葡萄糖基转移酶(UDP-glucosyltransferase, UGT)基因MpUGT1的编码区进行克隆,并通过在线服务器分析该基因的生物信息学特性;利用实时荧光定量PCR方法检测了MpUGT1基因在布渣叶的芽、叶、枝、果、花不同部位的表达情况。结果表明,本研究克隆得到的布渣叶MpUGT1基因,其cDNA全长为1 397 bp,ORF 1 377 bp,编码458个氨基酸,GenBank登陆号为KY652922。生物信息学预测分析该基因编码蛋白质分子式为C2324H3643N603O671S18,相对分子质量为51 kD,理论等电点(PI)为5.99,不稳定系数为43.81,亲水性系数为-0.105。该蛋白没有跨膜结构域,含有UDP-葡萄糖醛酸/UDP-葡萄糖基转移酶家族保守结构域,不含信号肽,定位于叶绿体。RT-qPCR组织特异性表达分析结果表明MpUGT1在芽、叶、枝、果、花中均有表达,且叶的表达量最高。系统进化树分析显示Mp UGT1与同科植物黄麻、长蒴黄麻等同源UGT的相似度最高,均达到了约80%;上述结果为进一步研究该基因在布渣叶黄酮苷生物合成中的作用奠定了基础。     

Combined effects of the UGT1A1 and OATP2 gene polymorphisms as major risk factor for unconjugated hyperbilirubinemia in Indian neonates

Genetic association studies have linked a number of single nucleotide polymorphisms (SNPs) with unconjugated hyperbilirubinemia. The present study was undertaken to validate the association of SNPs with development of hyperbilirubinemia in Indian neonates. Genotyping of five SNPs in two candidate genes was performed in 126 infants with hyperbilirubinemia and 181 controls by PCR-RFLP, Gene Scan analysis and direct DNA sequencing. Genetic polymorphisms of the UGT1A1 promoter, specifically the − 3279 T ? G phenobarbital responsive enhancer module (rs4124874) and (TA)7 dinucleotide repeat (rs8175347) as well as the coding region variants (rs2306283 and rs4149056) of the OATP2 gene were significantly higher among the cases than the controls. The presence of the mutant haplotypes either in homozygous, heterozygous or compound heterozygous state had a significant effect on neonatal hyperbilirubinemia as well as on the requirement of phototherapy than those with the wild haplotype. Further, a significantly higher number of hyperbilirubinemic cases had ≥ 3 variants than the controls (73.80% vs 40.36%, p < 0.0001) and the mean total serum bilirubin levels and requirement of phototherapy also increased according to the number of variants co-expressed. This study demonstrates that UGT1A1 and OATP2 polymorphisms were associated with altered bilirubin metabolism and could be genetic risk factors for neonatal hyperbilirubinemia.     

SIS8, a putative mitogen‐activated protein kinase kinase kinase,regulates sugar‐resistant seedling development in Arabidopsis

Sugar signaling pathways have been evolutionarily conserved among eukaryotes and are postulated to help regulate plant growth, development and responses to environmental cues. Forward genetic screens have identified sugar signaling or response mutants. Here we report the identification and characterization of Arabidopsis thaliana sugar insensitive8 (sis8) mutants, which display a sugar‐resistant seedling development phenotype. Unlike many other sugar insensitive mutants, sis8 mutants exhibit wild‐type responses to the inhibitory effects of abscisic acid and paclobutrazol (an inhibitor of gibberellin biosynthesis) on seed germination. Positional cloning of the SIS8 gene revealed that it encodes a putative mitogen‐activated protein kinase kinase kinase (MAPKKK; At1g73660). SIS8mRNA is expressed ubiquitously among Arabidopsis organs. A UDP‐glucosyltransferase, UGT72E1 (At3g50740), was identified as an interacting partner of SIS8 based on a yeast two‐hybrid screen and in planta bimolecular fluorescence complementation. Both SIS8–yellow fluorescent protein (YFP) and UGT72E1–YFP fusion proteins localize to the nucleus when transiently expressed in tobacco leaf cells. T‐DNA insertions in At3g50740 cause a sugar‐insensitive phenotype. These results indicate that SIS8, a putative MAPKKK, is a regulator of sugar response in Arabidopsis and interacts with a UDP‐glucosyltransferase in the nucleus.