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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mutants requiring S-adenosyl methionine (SAM) for growth have been selected in Saccharomyces cerevisiae. Two classes of mutants have been found. One class corresponds to the simultaneous occurrence of mutations at two unlinked loci SAM1 and SAM2 and presents a strict SAM requirement for growth on any medium. The second class corresponds to special single mutations in the gene SAM2 which lead to a residual growth on minimal medium but to normal growth on SAM supplemented medium or on a complex medium like YPGA not containing any SAM. These genetic data can be taken as an indication that Saccharomyces cerevisiae possesses two isoenzymatic methionine adenosyl transferases (MAT). In addition, SAM1 and SAM2 loci have been identified respectively with the ETH-10 and ETH2 loci previously described. Biochemical evidences corroborate the genetic results. Two MAT activities can be dissociated in a wild type extract (MATI and MATII) by DEAE cellulose chromatography. Mutations at the SAM1 locus lead to the absence or to the modification of MATII whereas mutations at the SAM2 locus lead to the absence or to the modification of MATI. Moreover, some of our results seem to show that MATI and MATII are associated in vivo.
Mol Gen Genet 1978 Jul 11
PMID:S-adenosyl methionine requiring mutants in Saccharomyces cerevisiae: evidences for the existence of two methionine adenosyl transferases. 35 45

Some metK mutants of Salmonella typhimurium with constitutive methionine biosynthesis have no detectable S-adenosylmethionine (SAM) synthetase, the enzyme which converts methionine to SAM, the postulated corepressor of the methionine pathway. However, these mutants are not auxotrophic for SAM, an essential compound for many reactions.
Mol Gen Genet 1976 Feb 27
PMID:The synthesis of S-adenosylmethionine by mutants with defects in S-adenosylmethionine synthetase. 77 17

Saccharomyces cerevisiae strain 83384-B3 carries the sai-1 mutation which confers sensitivity to S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH). It was shown that the mutant is impermeable to precursors of ribonucleic acid (RNA) and protein during inhibition by SAM (0.2 mM). Inhibition of uptake of adenine and uracil was nearly complete 3 h after growth in the presence of SAM and the uptake of leucine was at least 10-fold lower. The incorporation of 3H-adenine into ribosomal RNA, transfer RNA and heterodisperse RNA, believed to be messenger, was reduced 10-fold when measured after 1 h inhibition. The inhibition of growth was completely reversed by methionine (2.0 mM) in cells previously exposed to SAM for 90 min. The polysome content in cells inhibited by SAM was 25% less than the control after 4 h inhibition. Ribosome synthesis increased only about 40% in the presence of SAM and about 5-fold in the control over an 8 h period. All classes of RNA were synthesized during inhibition.
Mol Gen Genet 1976 Mar 30
PMID:Macromolecule synthesis in a mutant of Saccharomyces cerevisiae inhibited by S-adenosyimethionine. 77 1

E. coli SK has its own enzyme system providing DNA host specificity which differs from the known types of specificity in E. coli K12 and E. coli B. Modification and restriction are observed when the PBVI or PBV3 phages are transferred from E. coli SK to E. coli B or K12 (and back). A methylase has been isolated from E. coli SK cells and partly purified. This methylase catalyzes in vitro transfer of the labelled methyl groups from S-adenosylmethionine (SAM) to DNA of both phage and tissue origin which gives rise to 5'-methylcytosine (5'MC) and 6'-methylaminopurine (6'MAP). The methylase preparations isolated from the cells at the stationary growth have proved to be 1.5-1.7 times as active as the enzyme from the cells at the logarithmic growth stage. The extract of E. coli SK cells infected with the phage SD cannot methylate DNA in vitro. This fact is due to de novo synthesis of the enzyme which disintegrates SAM down to 5'-methyltioadenosine (5'MTA) and homoserine (HS). This enzyme is not found in the cells infected with the SD phage in the presence of chloroamphenicole. The activity of the enzyme which disintegrates SAM is the highest between the 4th and the 5th minutes of infection. Thus it may be assumed that this enzyme, most probably, is an early virus specific protein and prevents in vivo methylation of the phage DNA.
Mol Cell Biochem 1976 Nov 30
PMID:The host specificity system in Escherichia coli SK. 79 97

The enzymes involved in host-controlled modification and restriction by Bacillus subtilis strain N were detected in cell free extracts. In the presenct of Mg2+ the N-specific endonucleases cleaved unmodified DNA but did not attack phi-105C. N DNA carrying N-specific modification. The restriction endonuclease required neither SAM nor ATP for its activity. The N-specific modification enzyme was active only in the presence of SAM, indicating that modification in this syteem is a methylation of DNA.
Mol Gen Genet 1975 Jul 10
PMID:In vitro modification and restriction of phage phi-105c DNA with Bacillus subtilis N cell-free extract. 80 94

GpppG was modified to m7 GpppGm by a cytoplasmic extract, prepared from embryonic lens cells, in a reaction mixture which contained S-adenosyl-methionine as methyl group donor. The appearance of m7 GpppGm was a function of time and lens extract concentration. S-adenosyl-homocysteine inhibited both the m7G and Gm modification reactions. Analogues of GpppG, pG, ppG and pppG were relatively ineffective as substrates.
Mol Biol Rep 1977 Jun
PMID:Detection of methyltransferase activities which modify Gppp G to m7GpppGm in embryonic chick lens. 88 98

Saccharomyces cerevisiae cells that are mutated at TOP3, a gene that encodes a protein homologous to bacterial type I topoisomerases, have a variety of defects, including reduced growth rate, altered gene expression, blocked sporulation, and elevated rates of mitotic recombination at several loci. The rate of ectopic recombination between two unlinked, homologous loci, SAM1 and SAM2, is sixfold higher in cells containing a top3 null mutation than in wild-type cells. Mutations in either of the two other known topoisomerase genes in S. cerevisiae, TOP1 and TOP2, do not affect the rate of recombination between the SAM genes. The top3 mutation also changes the distribution of recombination events between the SAM genes, leading to the appearance of novel deletion-insertion events in which conversion tracts extend beyond the coding sequence, replacing the DNA flanking the 3' end of one SAM gene with nonhomologous DNA flanking the 3' end of the other. The effects of the top3 null mutation on recombination are dependent on the presence of an intact RAD1 excision repair gene, because both the rate of SAM ectopic gene conversion and the conversion tract length were reduced in rad1 top3 mutant cells compared with top3 mutants. These results suggest that a RAD1-dependent function is involved in the processing of damaged DNA that results from the loss of Top3 activity, targeting such DNA for repair by recombination.
Mol Cell Biol 1992 Nov
PMID:Genome rearrangement in top3 mutants of Saccharomyces cerevisiae requires a functional RAD1 excision repair gene. 132 69

Oligodeoxynucleotides 18 nucleotides in length having sequences complementary to regions spanning the initiation codon regions of ornithine decarboxylase or S-adenosylmethionine decarboxylase mRNAs were tested for their ability to inhibit translation of these mRNAs. In reticulocyte lysates, a strong and dose dependent reduction of ornithine decarboxylase synthesis in response to mRNA from D-R L1210 cells was brought about by 5'-AAAGCTGCTCATGGTTCT-3' which is complementary to the sequence from -6 to +12 of the mRNA sequence but there was no inhibition by 5'-TGCAGCTTCCATCACCGT-3'. Conversely, the latter oligodeoxynucleotide which is complementary to the sequence from -6 to +12 of the mRNA of S-adenosyl methionine decarboxylase was a strong inhibitor of the synthesis of this enzyme in response to rat prostate mRNA and the antisense sequence from ornithine decarboxylase had no effect. The translation of ornithine decarboxylase mRNA in a wheat germ system was inhibited by the antisense oligodeoxynucleotide at much lower concentration than those needed in the reticulocyte lysate suggesting that degradation of the hybrid by ribonuclease H may be an important factor in this inhibition. These results indicate that such oligonucleotides may be useful to regulate cellular polyamine levels and as probes to study control of mRNA translation.
Mol Cell Biochem 1992 Dec 16
PMID:Inhibition of ornithine decarboxylase and S-adenosylmethionine decarboxylase synthesis by antisense oligodeoxynucleotides. 133 19

The Trypanosoma brucei spliced leader (SL) RNA donates its 5' leader sequence to all nuclear pre-mRNAs via trans RNA splicing. The SL RNA is a small-nuclear U RNA-like molecule which is present in the cell as part of a small ribonucleoprotein particle. However, unlike the trimethylguanosine-capped small nuclear U RNAs, the SL RNA has a highly modified 5' terminus containing an m7G cap and methylations on the first four transcribed nucleotides. Here, we show that incubation of procyclic-form T. brucei in the presence of the S-adenosylmethionine analog, sinefungin, leads to a rapid inhibition of SL RNA methylation. A concomitant inhibition of trans splicing and an accumulation of high-molecular-weight tubulin transcripts were also observed. The effects of sinefungin on SL RNA methylation and on trans splicing were correlated by labeling of cells incubated in the presence of the antibiotic. The results indicate that 5' modifications of the SL RNA are necessary for it to participate in trans splicing. SL RNA modification is not required for assembly of the core SL ribonucleoprotein, as these Cs2SO4-resistant particles can be formed with either methylated or undermethylated SL RNA.
Mol Cell Biol 1992 Nov
PMID:Trypanosoma brucei spliced-leader RNA methylations are required for trans splicing in vivo. 140 66

Trypanosoma brucei brucei contained a S-adenosyl-L-methionine decarboxylase (AdoMetDC) strongly activated by putrescine. The enzyme was also activated to a lesser extent by cadaverine and 1,3-diaminopropane. Spermidine and spermine had no effect on basal activity of the enzyme. However, they interfered with putrescine activation of trypanosomal AdoMetDC. The trypanosomal enzyme could not be precipitated with antiserum against human AdoMetDC. The trypanosomal AdoMetDC enzyme subunit was labeled by reaction with 35S-decarboxylated AdoMet in the presence of NaCNBH4, and found to have a molecular weight of 34 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The subunit was readily degraded on storage to a form with a molecular weight of 26 kDa. The specificity of labeling of AdoMetDC by this procedure was confirmed by the prevention of 35S-decarboxylated S-adenosylmethionine (AdoMet) binding in the presence of specific AdoMetDC inhibitors [either methylglyoxal bis(guanylhydrazone (MGBG), a reversible inhibitor, or 5'-deoxy-5'-[(2-hydrazinoethyl)methylamino]adenosine (MHZEA), an irreversible inactivator]. As compared to human AdoMetDC, the trypanosomal enzyme showed weaker binding to a column of MGBG-Sepharose and also was significantly less sensitive to inhibition by MGBG and its congener ethylglyoxal bis(guanylhydrazone) (EGBG). Thus, the trypanosomal AdoMetDC differs significantly from its mammalian and bacterial counterparts and may therefore be exploited as a specific target for chemotherapy of trypanosomiasis.
Mol Cell Biochem 1992 Nov 04
PMID:Putrescine activated S-adenosylmethionine decarboxylase from Trypanosoma brucei brucei. 148 Jan 64


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