ATP Depletion Affects the Phosphorylation State, Ligand Binding, and Nuclear Transport of the 4 S Polycyclic Aromatic Hydrocarbon-binding Protein in Rat Hepatoma Cells

Bhat, Rashid; Weaver, James; Wagner, Conrad; Bodwell, Jack E.; Bresnick, Edward

doi:10.1074/jbc.271.51.32551

Cited by 24 publications

(21 citation statements)

References 46 publications

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“…The Bresnick group suggested that GNMT is the putative "4 S" aryl hydrocarbon receptor responsible for induction of cytochrome P-450 1A (CYP1A) by benzo-(a)pyrene that is translocated to the nucleus (9). Other studies have questioned the role of GNMT as the 4 S aryl hydrocarbon receptor (8).…”

Section: Gnmt Genes and Proteinsmentioning

confidence: 99%

Glycine N-Methyltransferase and Regulation of S-Adenosylmethionine Levels

Luka

Mudd

Wagner

2009

Journal of Biological Chemistry

Self Cite

174

155

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Methylation is a major biological process. It has been shown to be important in formation of compounds such as phosphatidylcholine, creatine, and many others and also participates in epigenetic effects through methylation of histones and DNA. The donor of methyl groups for almost all cellular methylation reactions is S-adenosylmethionine. It seems that the level of S-adenosylmethionine must be regulated in response to developmental stages and metabolic changes, and the enzyme glycine N-methyltransferase has been shown to play a major role in such regulation in mammals. This minireview will focus on the latest discoveries in the elucidation of the mechanism of that regulation. Discovery of S-Adenosylmethionine and Its VersatilityAdoMet 2 was discovered in 1951 by Cantoni as the "active methionine" used in the enzymatic transfer of the methyl group of methionine to nicotinamide to form N 1 -methylnicotinamide (1). With the exception of a few intracellular parasites that take up AdoMet from their hosts, AdoMet is formed from ATP and methionine by methionine adenosyltransferases present in all (or virtually all) cells of all organisms, including archaea, eubacteria, and eukaryotes. The reaction involves, initially, transfer of the adenosyl group of ATP to methionine, with the remainder of the ATP being converted to enzyme-bound tripolyphosphate. The latter compound is hydrolyzed to pyrophosphate and phosphate, which are then released (2). Being a sulfonium compound, AdoMet provides the large amounts of free energy (20 ϳkcal/mol) needed for methyl group transfers.AdoMet is possibly the most (or, compared with ATP, the second most) versatile compound in Nature. It is a source not only of methyl groups but, in diverse reactions in various organisms, provides methylene groups, four-carbon moieties, ribosyl groups, amino groups, and, after decarboxylation, threecarbon moieties for polyamines and ethylene (3). It may be converted to a 5Ј-deoxyadenosyl free radical that participates in a great variety of "radical SAM" reactions (4). AdoMet also functions as a regulator of many metabolic pathways in mammals, plants, and bacteria.In mammals, Ͼ90% of AdoMet is used for methylation reactions by at least 50 different methyltransferases (5). Methylation of both small molecules (e.g. phosphatidylethanolamine and guanidinoacetate) and macromolecules (DNA, RNA, histones, and other proteins) plays critical roles in cellular metabolism. Methylations of DNA and histones are major events in epigenetics. Therefore, the level of AdoMet must be carefully regulated to maintain cellular homeostasis. Recent evidence has established that GNMT plays a major role in maintaining normal AdoMet levels in mammals. GNMT Genes and ProteinsIn 1960, enzymatically catalyzed direct transfer of a methyl group from AdoMet to glycine (forming sarcosine) was demonstrated. The activity was found in liver extracts from guinea pig, rat, rabbit, and mouse, but the enzyme was not purified until 1972 when Heady and Kerr, upon finding that glycine was a better acce...

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Section: Gnmt Genes and Proteinsmentioning

confidence: 99%

Glycine N-Methyltransferase and Regulation of S-Adenosylmethionine Levels

Luka

Mudd

Wagner

2009

Journal of Biological Chemistry

Self Cite

174

155

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“…7). In one experiment, cells were incubated for 90 min with 20 mM NaN 3 (19) in DMEM͞10% serum and subjected to FCS (see below) in Leibovitz L-15 (GIBCO͞BRL) medium containing 20 mM NaN 3 .…”

Section: Methodsmentioning

confidence: 99%

Intranuclear diffusion and hybridization state of oligonucleotides measured by fluorescence correlation spectroscopy in living cells

Politz

Browne

Wolf

et al. 1998

Proc. Natl. Acad. Sci. U.S.A.

253

209

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Fluorescein-labeled oligodeoxynucleotides (oligos) were introduced into cultured rat myoblasts, and their molecular movements inside the nucleus were studied by f luorescence correlation spectroscopy (FCS) and f luorescence recovery after photobleaching (FRAP). FCS revealed that a large fraction of both intranuclear oligo(dT) (43%) and oligo(dA) (77%) moves rapidly with a diffusion coefficient of 4 ؋ 10 ؊7 cm 2 ͞s. Interestingly, this rate of intranuclear oligo movement is similar to their diffusion rates measured in aqueous solution. In addition, we detected a large fraction (45%) of the intranuclear oligo(dT), but not oligo(dA), diffusing at slower rates (<1 ؋ 10 ؊7 cm 2 ͞s). The amount of this slower-moving oligo(dT) was greatly reduced if the oligo(dT) was prehybridized in solution with (unlabeled) oligo(dA) prior to introduction to cells, presumably because the oligo(dT) was then unavailable for subsequent hybridization to endogenous poly(A) RNA. The FCS-measured diffusion rate for much of the slower oligo(dT) population approximated the diffusion rate in aqueous solution of oligo(dT) hybridized to a large polyadenylated RNA (1.0 ؋ 10 ؊7 cm 2 ͞s). Moreover, this intranuclear movement rate falls within the range of calculated diffusion rates for an average-sized heterogeneous nuclear ribonucleoprotein particle in aqueous solution. A subfraction of oligo(dT) (15%) moved over 10-fold more slowly, suggesting it was bound to very large macromolecular complexes. Average diffusion coefficients obtained from FRAP experiments were in agreement with the FCS data. These results demonstrate that oligos can move about within the nucleus at rates comparable to those in aqueous solution and further suggest that this is true for large ribonucleoprotein complexes as well.An understanding of the physical environment inside the cell nucleus is central to a coherent view of gene expression. It is important to know how the viscosity and molecular diffusion rates in the nucleus of a living cell compare with experimental conditions in vitro, where interactions between nucleic acids and proteins are studied at high dilution in aqueous solution. For example, it is not clear whether ribonucleoprotein (RNP) complexes can diffuse freely about the nucleus, impeded only by locally high concentrations of macromolecules or, alternatively, are bound or compartmentalized in such a way as to constrain their motion. Some observations suggest that premRNA transcripts are tethered to elements of the transcriptional, splicing, and͞or polyadenylation machinery (1-3), and it has been proposed that processed mRNAs make their way out of the nucleus by molecular diffusion (4, 5). However, mediated processes have not been ruled out, and the functional relationships between RNA export and nuclear structure remain unclear (6).Recently, Politz et al. (7) characterized nucleic acid uptake and hybridization in living cells by in situ reverse transcription and found that fluorescently labeled oligo(dT) can be taken up by living cells and form hybrid...

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“…Intriguingly, we observed similar reorganization and dynamic properties of RSZp22 upon ATP depletion, which might suggest that the absence of RSZp22 mobility upon ATP depletion is linked to its phosphorylation state. ATP depletion could indeed alter many cellular mechanisms, including changes in the phosphorylation levels of proteins and changes in protein interactions (Bhat et al, 1996), which could in turn modulate and modify the dynamic properties of SR proteins.…”

Section: Nuclear Functional Dynamics Of Arabidopsis Sr Proteinsmentioning

confidence: 99%

Insights into Nuclear Organization in Plants as Revealed by the Dynamic Distribution ofArabidopsisSR Splicing Factors

et al. 2006

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Serine/arginine-rich (SR) proteins are splicing regulators that share a modular structure consisting of one or two N-terminal RNA recognition motif domains and a C-terminal RS-rich domain. We investigated the dynamic localization of the Arabidopsis thaliana SR protein RSZp22, which, as we showed previously, distributes in predominant speckle-like structures and in the nucleolus. To determine the role of RSZp22 diverse domains in its nucleolar distribution, we investigated the subnuclear localization of domain-deleted mutant proteins. Our results suggest that the nucleolar localization of RSZp22 does not depend on a single targeting signal but likely involves different domains/motifs. Photobleaching experiments demonstrated the unrestricted dynamics of RSZp22 between nuclear compartments. Selective inhibitor experiments of ongoing cellular phosphorylation influenced the rates of exchange of RSZp22 between the different nuclear territories, indicating that SR protein mobility is dependent on the phosphorylation state of the cell. Furthermore, based on a leptomycin B-and fluorescence loss in photobleaching-based sensitive assay, we suggest that RSZp22 is a nucleocytoplasmic shuttling protein. Finally, with electron microscopy, we confirmed that RSp31, a plant-specific SR protein, is dynamically distributed in nucleolar cap-like structures upon phosphorylation inhibition. Our findings emphasize the high mobility of Arabidopsis SR splicing factors and provide insights into the dynamic relationships between the different nuclear compartments.

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ATP Depletion Affects the Phosphorylation State, Ligand Binding, and Nuclear Transport of the 4 S Polycyclic Aromatic Hydrocarbon-binding Protein in Rat Hepatoma Cells

Cited by 24 publications

References 46 publications

Glycine N-Methyltransferase and Regulation of S-Adenosylmethionine Levels

Glycine N-Methyltransferase and Regulation of S-Adenosylmethionine Levels

Intranuclear diffusion and hybridization state of oligonucleotides measured by fluorescence correlation spectroscopy in living cells

Insights into Nuclear Organization in Plants as Revealed by the Dynamic Distribution ofArabidopsisSR Splicing Factors

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