Effects of S-adenosylhomocysteine analogs on vaccinia viral mRNA synthesis and methylation

Pugh, Charles; Borchardt, Ronald T.

doi:10.1021/bi00536a011

Cited by 65 publications

(45 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…SAM, at least within physiologic ranges of homocysteine. Cellular methyltransferases that have been shown experimentally to be inhibited by SAH include catecholamine-O-methyltransferase (39), phosphatidylethanolamine methyltransferase (46), histone methyltransferase (18), DNA methyltransferase (18,26,47), tRNA and mRNA methyltransferases (48,49), acetylserotonin methyltransferase (50), and histamine N-methyltransferase (51). The functional consequences of decreased cellular methylation are significant and include central nervous system demyelination (52,53), reduced neurotransmittor synthesis (39,50), decreased chemotaxis and macrophage phagocytosis (54,55), altered membrane phospholipid composition and membrane fluidity (56,58), altered gene expression (23,59,60), and cell differentiation (61,62).…”

Section: Discussionmentioning

confidence: 99%

Increase in Plasma Homocysteine Associated with Parallel Increases in Plasma S-Adenosylhomocysteine and Lymphocyte DNA Hypomethylation

Melnyk

Pogribna

et al. 2000

Journal of Biological Chemistry

590

381

View full text Add to dashboard Cite

An elevation in plasma homocysteine is a sensitive but nonspecific biomarker for an imbalance in the integrated pathways of one-carbon metabolism (1, 2). Chronic nutritional deficiencies in folate, choline, methionine, vitamin B 6 , and/or vitamin B 12 can perturb the complex regulatory network that maintains normal one-carbon metabolism and homocysteine homeostasis (3-7). Genetic polymorphisms in these pathways can act synergistically with nutritional deficiencies to accelerate the metabolic pathology associated with chronic disease states (8). Although several hypotheses have been proposed to explain the association between hyperhomocysteinemia and the thrombotic/atherosclerotic process occurring with occlusive cardiovascular disease, as yet none has been definitive (9 -12). Similarly, increases in plasma homocysteine concentrations have been associated with increased risk of certain birth defects (13-16), but the underlying mechanism remains elusive. A major unanswered question is whether direct cellular toxicity of homocysteine is causally involved in pathogenesis or whether homocysteinemia is simply a passive and indirect indicator of a more complex mechanism.Homocysteine is derived solely from methionine metabolism and is significantly recycled to conserve sufficient methionine for protein and S-adenosylmethionine synthesis. The interactive and interdependent pathways of the methionine/homocysteine cycle are diagrammed in Fig. 1 to emphasize the indirect effects of pathway perturbations on cellular methyltransferase reactions. The metabolic generation of homocysteine from methionine is initiated by the ATP-dependent transfer of adenosine to methionine via methionine adenosyltransferase. The product, S-adenosylmethionine (SAM), 1 is a priority for onecarbon metabolism because it is the methyl donor for most cellular methyltransferase reactions. In addition to DNA methylation, SAM-dependent methyltransferase activity is essential for hundreds of other cellular methylation reactions including synthesis of creatine in the liver, membrane phosphatidylcholine synthesis, central nervous system neurotransmittor synthesis, methylation/detoxification, and RNA and protein methylation (17). After transfer of the methyl group, SAM is converted to S-adenosylhomocysteine (SAH) within the active site of the methyltransferase enzyme. Because most methyltransferases bind SAH with higher affinity than SAM, they are subject to potent product inhibition by SAH (18). Thus, the efficiency of methyltransferase reactions is absolutely dependent on efficient product removal of SAH. This is effectively accomplished by SAH hydrolase (SAHH), an enzyme that appears to act in close proximity to the methyltransferases, at least in the nucleus (19). The crystal structure of SAHH has been recently reported, and interestingly, the polypeptide folding pattern at the catalytic domain of SAHH is almost identical to that reported for the DNA methyltransferases and suggests that SAH molecules can travel easily between the catalytic pockets of th...

show abstract

Section: Discussionmentioning

confidence: 99%

Increase in Plasma Homocysteine Associated with Parallel Increases in Plasma S-Adenosylhomocysteine and Lymphocyte DNA Hypomethylation

Melnyk

Pogribna

et al. 2000

Journal of Biological Chemistry

590

381

View full text Add to dashboard Cite

show abstract

“…We tested various AdoMet analogues (see Methods), among them molecules with proven viral mRNA cap MTase inhibition capacity, such as the reaction product AdoHcy (Pugh & Borchardt, 1982) and sinefungin (Dong et al, 2008a;Li et al, 2007;Pugh et al, 1978), but also molecules inhibiting other AdoMet-dependent MTases, such as 59-S-isobutylthio-59-deoxyadenosine (SIBA), 3-deaza-adenosine (Kloor et al, 2004) and 59-deoxy-59-methylthio-adenosine (MTA) (Woodcock et al, 1983), or simply analogues of adenosine (29,39,59-tri-O-acetyl-adenosine) and AdoMet. We also used three GTP analogues: broad-spectrum antiviral ribavirin and its triphosphate, as well as 5-ethynyl-1-b-Dribofuranosylimidazole-4-carboxamide) (EICAR) triphosphate.…”

Section: Inhibition Of Ns5mtase DV 2 §O-mtase Activitymentioning

confidence: 99%

Biochemical characterization of the (nucleoside-2'O)-methyltransferase activity of dengue virus protein NS5 using purified capped RNA oligonucleotides 7MeGpppACn and GpppACn

Selisko

Peyrane

Canard

et al. 2009

Journal of General Virology

View full text Add to dashboard Cite

The flavivirus RNA genome contains a conserved cap-1 structure, 7Me GpppA 29OMe G, at the 59 end. Two mRNA cap methyltransferase (MTase) activities involved in the formation of the cap, the (guanine-N7)-and the (nucleoside-29O)-MTases (29O-MTase), reside in a single domain of nonstructural protein NS5 (NS5MTase). This study reports on the biochemical characterization of the 29O-MTase activity of NS5MTase of dengue virus (NS5MTase DV ) using purified, short, capped RNA substrates ( 7Me GpppAC n or GpppAC n ). NS5MTase DV methylated both types of substrate exclusively at the 29O position. The efficiency of 29O-methylation did not depend on the methylation of the N7 position. Using 7Me GpppAC n and GpppAC n substrates of increasing chain lengths, it was found that both NS5MTase DV 29O activity and substrate binding increased before reaching a plateau at n55. Thus, the cap and 6 nt might define the interface providing efficient binding of enzyme and substrate. K m values for 7Me GpppAC 5 and the co-substrate S-adenosyl-Lmethionine (AdoMet) were determined (0.39 and 3.26 mM, respectively). As reported for other AdoMet-dependent RNA and DNA MTases, the 29O-MTase activity of NS5MTase DV showed a low turnover of 3.25¾10 "4 s "1 . Finally, an inhibition assay was set up and tested on GTP and AdoMet analogues as putative inhibitors of NS5MTase DV , which confirmed efficient inhibition by the reaction product S-adenosyl-homocysteine (IC 50 0.34 mM) and sinefungin (IC 50 0.63 mM), demonstrating that the assay is sufficiently sensitive to conduct inhibitor screening and characterization assays. INTRODUCTIONMost eukaryotic and viral mRNAs are modified by the addition of a cap structure at the 59 end. The mRNA cap consists of an N7-methylguanosine linked to the first transcribed nucleotide by a 59-59 triphosphate bridge (cap-0 structure, 7Me GpppN) (Shuman, 2001). Methylation of the 29O positions of the ribose of the first or the second transcribed nucleotide leads to a cap-1 ( 7Me GpppN 29OMe ) or cap-2 ( 7Me GpppN 29OMe N 29OMe ) structure, respectively. The cap structure stabilizes mRNA and plays a vital role in its translation by controlling mRNA splicing, its transport across the nuclear membrane and its recognition by the eIF4E translation factor (Furuichi & Shatkin, 2000). In eukaryotic cells, the acquisition of the cap-0 structure is a co-transcriptional event. RNA capping implies three steps in which the 59 triphosphate end of RNA is hydrolysed to a 59 diphosphate by an RNA triphosphatase (RTPase), then capped with GMP by a guanylyltransferase (GTase) and finally methylated at the N7 position of the guanine by an S-adenosyl-L-methionine (AdoMet)-dependent (guanine-N7)-methyltransferase (N7-MTase) (Gu & Lima, 2005). In contrast to mRNAs of lower eukaryotes, which bear a cap-0 structure, the mRNAs of higher eukaryotes acquire a cap-1 structure via the action of a (nucleoside-29O)-MTase (29O-MTase) (Langberg & Moss, 1981). Compared with N7 methylation, this mRNA methylation step seems to be less important for binding, tr...

show abstract

“…Many biological activities of sinefungin are believed to be related to the inhibition of S-adenosylmethionine-dependent methyltransferase enzymes. [11][12][13][14][15][16] When administered intraperitoneally, sinefungin cures mice infected with T. brucei brucei, Trypanosoma congolense and Trypanosoma vivax. 17,18 It was well tolerated in mice, and when the dose per injection was 0.05-5 mg kg À1 , sinefungin was highly effective against African trypanosomes.…”

Section: Discussionmentioning

confidence: 99%

Sinefungin VA and dehydrosinefungin V, new antitrypanosomal antibiotics produced by Streptomyces sp. K05-0178

et al. 2010

View full text Add to dashboard Cite

Two new nucleotide antibiotics, named sinefungin VA and dehydrosinefungin V, were separated by cation exchange column chromatography and purified by HPLC from the culture broth of Streptomyces sp. K05-0178, together with the known antibiotics, sinefungin, dehydrosinefungin and KSA-9342. The structures of the two novel sinefungin analogs were elucidated by spectroscopic studies, including various NMR and advanced peptide chemical methods. Sinefungin VA consists of adenosine and ornithylvalylalanine, whereas dehydrosinefungin V consists of 4¢,5¢-dehydroadenosine and ornithylvaline. Sinefungin VA showed potent antitrypanosomal activity with an IC 50 value of 0.0026 lg ml À1 in vitro without cytotoxicity against MRC-5 cells. Dehydrosinefungin V showed moderate antitrypanosomal activity (IC 50 ¼0.15 lg ml À1 ).

show abstract

Effects of S-adenosylhomocysteine analogs on vaccinia viral mRNA synthesis and methylation

Cited by 65 publications

References 35 publications

Increase in Plasma Homocysteine Associated with Parallel Increases in Plasma S-Adenosylhomocysteine and Lymphocyte DNA Hypomethylation

Increase in Plasma Homocysteine Associated with Parallel Increases in Plasma S-Adenosylhomocysteine and Lymphocyte DNA Hypomethylation

Biochemical characterization of the (nucleoside-2'O)-methyltransferase activity of dengue virus protein NS5 using purified capped RNA oligonucleotides 7MeGpppACn and GpppACn

Sinefungin VA and dehydrosinefungin V, new antitrypanosomal antibiotics produced by Streptomyces sp. K05-0178

Contact Info

Product

Resources

About