Publications (17) View all
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Article: Lipidomic analysis of N-acylphosphatidylethanolamine molecular species in Arabidopsis suggests feedback regulation by N-acylethanolamines.
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ABSTRACT: N-Acylphosphatidylethanolamine (NAPE) and its hydrolysis product, N-acylethanolamine (NAE), are minor but ubiquitous lipids in multicellular eukaryotes. Various physiological processes are severely affected by altering the expression of fatty acid amide hydrolase (FAAH), an NAE-hydrolyzing enzyme. To determine the effect of altered FAAH activity on NAPE molecular species composition, NAE metabolism, and general membrane lipid metabolism, quantitative profiles of NAPEs, NAEs, galactolipids, and major and minor phospholipids for FAAH mutants of Arabidopsis were determined. The NAPE molecular species content was dramatically affected by reduced FAAH activity and elevated NAE content in faah knockouts, increasing by as much as 36-fold, far more than the NAE content, suggesting negative feedback regulation of phospholipase D-mediated NAPE hydrolysis by NAE. The N-acyl composition of NAPE remained similar to that of NAE, suggesting that the NAPE precursor pool largely determines NAE composition. Exogenous NAE 12:0 treatment elevated endogenous polyunsaturated NAE and NAPE levels in seedlings; NAE levels were increased more in faah knockouts than in wild-type or FAAH overexpressors. Treated seedlings with elevated NAE and NAPE levels showed impaired growth and reduced galactolipid synthesis by the "prokaryotic" (i.e., plastidic), but not the "eukaryotic" (i.e., extraplastidic), pathway. Overall, our data provide new insights into the regulation of NAPE-NAE metabolism and coordination of membrane lipid metabolism and seedling development.Planta 06/2012; 236(3):809-24. · 3.00 Impact Factor -
Article: Levels of Arabidopsis thaliana Leaf Phosphatidic Acids, Phosphatidylserines, and Most Trienoate-Containing Polar Lipid Molecular Species Increase during the Dark Period of the Diurnal Cycle.
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ABSTRACT: Previous work has demonstrated that plant leaf polar lipid fatty acid composition varies during the diurnal (dark-light) cycle. Fatty acid synthesis occurs primarily during the light, but fatty acid desaturation continues in the absence of light, resulting in polyunsaturated fatty acids reaching their highest levels toward the end of the dark period. In this work, Arabidopsis thaliana were grown at constant (21°C) temperature with 12-h light and 12-h dark periods. Collision induced dissociation time-of-flight mass spectrometry (MS) demonstrated that 16:3 and 18:3 fatty acid content in membrane lipids of leaves are higher at the end of the dark than at the end of the light period, while 16:1, 16:2, 18:0, and 18:1 content are higher at the end of the light period. Lipid profiling of membrane galactolipids, phospholipids, and lysophospholipids by electrospray ionization triple quadrupole MS indicated that the monogalactosyldiacylglycerol, phosphatidylglycerol, and phosphatidylcholine classes include molecular species whose levels are highest at end of the light period and others that are highest at the end of the dark period. The levels of phosphatidic acid (PA) and phosphatidylserine classes were higher at the end of the dark period, and molecular species within these classes either followed the class pattern or were not significantly changed in the diurnal cycle. Phospholipase D (PLD) is a family of enzymes that hydrolyzes phospholipids to produce PA. Analysis of several PLD mutant lines suggests that PLDζ2 and possibly PLDα1 may contribute to diurnal cycling of PA. The polar lipid compositional changes are considered in relation to recent data that demonstrate phosphatidylcholine acyl editing.Frontiers in plant science. 01/2012; 3:49. -
Article: Site-specific synthesis of oligonucleotides containing malondialdehyde adducts of deoxyguanosine and deoxyadenosine via a postsynthetic modification strategy.
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ABSTRACT: Malondialdehyde (MDA) and its reactive equivalent, base propenal, are products of oxidative damage to lipids and DNA, respectively; they are mutagenic in bacterial and mammalian systems, and MDA is carcinogenic in rats. MDA adducts of deoxyguanosine (M1dG), deoxyadenosine (OPdA), and deoxycytidine (OPdC) have been characterized. We have developed site-specific syntheses of M1dG and OPdA adducted oligonucleotides that rely on a postsynthetic modification strategy. This work provides an alternative route to the M1dG adducted oligonucleotide and, to date, the only viable strategy for the site-specific synthesis of OPdA-modified oligonucleotides. The stability of the modified oligonucleotides was examined by UV thermal melting studies (Tm). In contrast to the M1dG adduct, OPdA caused very little change in the Tm.Chemical Research in Toxicology 12/2006; 19(11):1467-74. · 3.78 Impact Factor -
Article: Evidence for Escherichia coli polymerase II mutagenic bypass of intrastrand DNA crosslinks.
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ABSTRACT: The mutagenic potentials of DNAs containing site- and stereospecific intrastrand DNA crosslinks were evaluated in Escherichia coli cells that contained a full complement of DNA polymerases or were deficient in either polymerases II, IV, or V. Crosslinks were made between adjacent N(6)-N(6) adenines and consisted of R,R- and S,S-butadiene crosslinks and unfunctionalized 2-, 3-, and 4-carbon tethers. Although replication of single-stranded DNAs containing the unfunctionalized 3- and 4-carbon tethers were non-mutagenic in all strains tested, replication past all the other intrastrand crosslinks was mutagenic in all E. coli strains, except the one deficient in polymerase II in which no mutations were ever detected. However, when mutagenesis was analyzed in cells induced for SOS, mutations were not detected, suggesting a possible change in the overall fidelity of polymerase II under SOS conditions. These data suggest that DNA polymerase II is responsible for the in vivo mutagenic bypass of these lesions in wild-type E. coli.DNA Repair 01/2006; 4(12):1374-80. · 4.14 Impact Factor -
Article: Mutagenic spectrum of butadiene-derived N1-deoxyinosine adducts and N6,N6-deoxyadenosine intrastrand cross-links in mammalian cells.
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ABSTRACT: Reactive metabolites of 1,3-butadiene, including 1,2-epoxy-3-butene (BDO), 1,2:3,4-diepoxybutane (BDO(2)), and 3,4-epoxy-1,2-butanediol (BDE), form both stable and unstable base adducts in DNA and have been implicated in producing genotoxic effects in rodents and human cells. N1 deoxyadenosine adducts are unstable and can undergo either hydrolytic deamination to yield N1 deoxyinosine adducts or Dimroth rearrangement to yield N(6) adducts. The dominant point mutation observed at AT sites in both in vivo and in vitro mutagenesis studies using BD and its epoxides has been A --> T transversions followed by A --> G transitions. To understand which of the butadiene adducts are responsible for mutations at AT sites, the present study focuses on the N1 deoxyinosine adduct at C2 of BDO and N(6),N(6)-deoxyadenosine intrastrand cross-links derived from BDO(2). These lesions were incorporated site-specifically and stereospecifically into oligodeoxynucleotides which were engineered into mammalian shuttle vectors for replication bypass and mutational analyses in COS-7 cells. Replication of DNAs containing the R,R-BDO(2) intrastrand cross-link between N(6) positions of deoxyadenosine yielded a high frequency (59%) of single base substitutions at the 3' adducted base, while 19% mutagenesis was detected using the S,S-diastereomer. Comparable studies using the R- and S-diastereomers of the N1 deoxyinosine adduct gave rise to approximately 50 and 80% A --> G transitions with overall mutagenic frequencies of 59 and 90%, respectively. Collectively, these data establish a molecular basis for A --> G transitions that are observed following in vivo and in vitro exposures to BD and its epoxides, but fail to reveal the source of the A --> T transversions that are the dominant point mutation.Chemical Research in Toxicology 12/2002; 15(12):1572-80. · 3.78 Impact Factor
